After speaking to the old woman in the Sealed Grounds, you reach Faron Woods.
Catch the Kikwi
Just past the entrance to Faron Woods, there is a rope hanging over a gap. Just press A to run to it, and Link will automatically grab it. Then swing the Wiimote to make Link swing. Press A to jump off of the rope to the other side.
There are some trees blocking the path. Use a vertical chop to get rid of them.
Just past that, there are a couple of red bokoblins harassing a forest creature. Kill the bokoblins and the creature will run away. Fi will then explain that the creature was a Kikwi. Fi detects a dowsing reading from the creature that is attuned to Zelda.
Run up the hill that the Kiwki ran up, and you will soon find the Kikwi, which will run away again. You will find a bird statue nearby, so save if you wish.
Use dowsing here to find the Kikwi. It is hiding behind the mushrooms nearby. Hit the mushroom with your sword to get the Kikwi to pop out again.
As you continue along, you will encounter some Deku Babas. Remember to slash in the appropriate direction according to how their mouths are shaped.
Eventually the Kikwi will hide behind a tree. Just talk to it this time. It will finally realize that you mean it no harm, and introduce itself as Machi. It will mention that another creature like you came through. She was being chased by red bokoblins, but she escaped with the Kikwi elder.
Find the Elder
Fi suggests using dowsing to find the elder.
When you dowse, you will see that you should go back the way you came. However, before you do, walk over to the nearby log and push it off of the ledge. This will give you a shortcut, and it will also reveal an Amber Relic.
Now go toward the dowsing signal. Dash up the watery ramp. Just run past the Deku Baba, then pick up a rock from the top of the hill and throw or roll it at the Deku Baba to kill it. Note that Deku Babas sometimes drop Jelly Blobs.
You will encounter some Red Bokoblins up ahead, and a Grass Octorok. To defeat the Octorok from a distance, thrust the Nunchuk forward to do a Shield Bash when the rock is about to hit. The rock will bounce off and hit the Octorok, killing it. If you don't do a Shield Bash when the rock hits you, your shield will be damaged.
Be sure to push the log off the ledge here to create another shortcut, where there is a bird statue nearby.
Go up the hill and do a vertical chop to get rid of more trees in the way. You will find a sealed door, and more enemies.
Soon you will reach a rope that is tied to a tuft of grass. Cut it, then hold A to dash forward and catch it. Swing the Wiimote to swing toward the far edge, then press A to jump off.
Go forward and talk to the big blob-like creature. This is Bucha, the Kikwi elder. He's too worried about the other missing Kikwis to talk about Zelda.
Find the Missing Kikwis
Fi will add the Kikwis as a dowsing option. Press and hold C to choose the Kikwis, then go look for them.
One of the readings is to the right of the elder, beyond the tree with the hollow spot at the bottom. One reading is behind the elder, and one is to the left. Start with the tree to the right.
Simply walk up to the hollow spot in the tree to the right and Link will automatically climb into the hole. Climb up the vines beyond. There is a rope ahead that you must walk along. The trick to balancing is to point your Wiimote up, then tilt it to the left or right to get Link to stay balanced on the rope. Keep tilting it left and right over and over rather than waiting for Link to lean too far. You can tilt the remote as soon as he goes off center to keep him from losing his balance.
There are also some burrs on the rope that will eventually explode if they latch onto Link, so be careful. You can follow the on screen instructions to try to shake them off.
Soon you reach a clearing where a Red Bokoblin will summon a gang of other Bokoblins. Fight them off, then the Kikwi will ask for help getting down from the tree. Fi will also give you some advice. To get it down, hold A to run toward the tree, then shake the Nunchuk to roll into the tree. The Kikwi will fall off the tree and introduce itself as Lopsa.
Walk up to the rope and press A to grab onto it. Climb up a little, then swing the Wiimote to swing toward the ledge, then press A to jump off. Push the log down, then hop down.
A Guay is nearby. They actually attack by pooping on your head. If this happens, it drains your stamina. Do a spin attack to get that stuff off of your head.
You will see a stone structure up ahead. There is a Red Bokoblin guarding it. Go up the stairs and you will find the symbol from the sealed door earlier, as well as a cave entrance that you can't reach. Go to the top of the stone structure to find a bird statue. Fi will recommend using this vantage point to dowse for Kikwis. One seems to be behind an area with a grey stone almost straight ahead, and the other seems to be on a ledge near a big brown rock.
Go down the stairs and head to the right. Some Guays and a Red Bokoblin will be there, so fight them off and continue along.
Up ahead, there will be three Bokoblins surrounding a tree. Kill them, then climb up the narrow ledge that you passed before reaching this clearing. At the end of the ledge you will see some vines. Dash up the wall to reach them, then flick the Wiimote when you reach the gap to leap over to the next section of vines. Be sure to grab the stamina fruit along the way. Then drop down when you reach the ledge.
There is a Kikwi hiding in the grass here. Cut the grass and the Kikwi will crawl around trying to hide. Keep cutting the grass until you get the option to talk to the Kikwi, named Erla.
Drop down from the ledge and find the hollow spot in the rocks past the tree where you fought the three Bokoblins. Crawl through, then use a shield bash to kill the Octorok nearby.
Then go to the right, where you can drop down a couple of ledges and push a log off of a tall ledge. This gives you yet another shortcut.
Go back the way you came. Another Octorok will be on the path ahead. You can go up a narrow slope and go to the left to find a rope leading to a Piece of Heart.
If you go in the other direction on the same narrow strip of land that took you to the Piece of Heart, you will find a tree near a brick wall. Near this tree, there is a hole in the ground. Drop down, then head through the narrow passageway to find a Kikwi hiding next to a regular tuft of grass. Try picking up the Kikwi and it will speak. It is called Oolo.
Get the Slingshot
Now go back and talk to the Elder. He will reveal that Zelda said that she had to go to the temple in the woods. The Elder says that she went toward the stone structure that you found earlier, with the bird statue at the top.
The Elder will give you the Slingshot. Just dash up the Elder's back to get it. To use it, press B. Then you can aim with the control stick. Press down on the control pad to center the cursor. Press A to shoot the slingshot. Press B again to put the Slingshot away.
Hop off of the Elder and he will say to shoot the curled-up vine with the slingshot. You can get more ammunition from the seeds of the fruit growing from the tree nearby.
Hit the curled-up vine with the slingshot and then use it to swing over to the other side. Swim across the small pond to get back to the Viewing Platform. Before heading into the temple, now is a good time to return to Skyloft, because you can now use the slingshot to get access to Beedle's Airshop.
Shop at Beedle's
Fly back to Skyloft, then follow Beedle's Airshop. When it gets close, use the slingshot to ring the bell. Beedle will lower a rope. Walk up to the rope and press A to grab it. The rope will lift you up onto the shop. Press A to let go of the rope, then go inside.
Buy a Bug Net. It's 50 rupees, which you probably have by now. You can also get an Extra Wallet for 100 rupees, so save up for that if you don't have enough yet. The other items are probably too expensive for you right now.
Now you can go around Skyloft and practice catching bugs. You can swing the net the same way that you swing the sword. Try moving the remote slowly to sweep the net toward the bugs. Quick slashes will only result in small movements of the net.
When you're ready, return to Faron Woods, going to the Viewing Platform location. There is a ledge in the back. Just shoot the slingshot at the rolled up vine above the entrance. Fi will have some advice. Press A near the vine to grab it, then climb up, swing the Wiimote to swing toward the ledge, then press A to jump over to the platform. Walk into the entrance. As you do, you'll see that a mysterious person is watching Link go through the entrance. Then Link will reach the Deep Woods.