After receiving the slingshot from the Kiwki Elder, you can reach the Deep Woods past Faron Woods.
Find a Goddess Cube
Upon entering the Deep Woods, you'll fight some Red Bokoblins just inside the entrance. You can knock the bee hive down with your slingshot, then use the bug net to catch the bees. You can purchase the bug net from Beedle's Airshop, which you can reach after you get the slingshot. Once you get rid of the bees, go over to where the hive fell and you will find Hornet Larvae.
You can also use the bug net on birds to get Bird Feathers. If you find a blue bird and use the net on it, you get a rare Blue Bird Feather.
Follow the stone path to the left of the tree. You'll reach a rope, but be sure to knock down the beehive before attempting to cross. If the bees follow you, catch them with the bug net. Then cross the rope.
As soon as you cross the rope, climb up the stairs to the left and push the log down off of the ledge to give yourself a shortcut. Go back the way you came and you will encounter a Red Bokoblin. Beyond that, there will be an Octorok. Once you defeat it, head down the dirt path to the right of where it was.
Dash up the wall to grab the ledge, and go across by hand. There will be a rope bridge, but there is a Bokoblin on the other side. Hit it with the slingshot, and it will start walking across the rope toward you. You might be able to get it to fall off by hitting it with the slingshot again. Otherwise, point your Wiimote up to charge up your sword, then lock onto the Bokoblin when it gets close enough, then swing the sword to unleash a Skyward Strike and kill the Bokoblin before it can reach you.
Avoid the grass just beyond the rope because it hides some explosive burrs. Then climb up the stairs, bash the tree to get some deku seeds, then kill the Deku Baba. Save at the bird statue here.
Dash toward the hanging rope, and swing the Wiimote to get yourself to the other side. There is a Quadro Baba here. Pay attention to its mouth shape, because it changes.
Before going over to the Goron, go up the ramp near the Quadro Baba to find a chest that contains 20 rupees.
Past the Quadro Baba, you will find the Goron from before. Talk to him until he tells you about the Goddess Cubes. The legend says to use the light from the heavenly blade to open the cubes. So point your sword up to charge it up, then hit the cube with a Skyward Strike. The cube will glow and then shoot up into the sky. This will unlock a treasure chest somewhere in the sky. The next time you return to the sky, Fi will show you the locations of the unlocked goddess cube chests.
Find another Goddess Cube
If you didn't get the red rupee from the chest nearby, go up the ramp near where you fought the Quadro Baba to find it. Then go down to the log near the Goron and push it over the ledge for another shortcut. Beyond where the log was, there are some short ledges that you can go down to reach the stone area beyond. There is another Goddess Cube down here, so be sure to hit it with a Skyward Strike to make it go up to the sky. As mentioned earlier, this will unlock a treasure chest somewhere in the sky. The next time you return to the sky, Fi will show you the locations of the unlocked goddess cube chests.
Now you can head toward the Forest Temple. When you get close to the Bird Statue, Fi will urge you to return to the sky if you need potions and a shield and other supplies before you go. Do so if you wish. You will be able to go directly to this bird statue, and any others that you have examined, the next time you dive into the green column of light in the sky.
Open the Skyview Temple
There is a sign to the right of the temple near a Deku Baba that tells you how to get into the temple. It says to aim your shot at the star that the bird gazes upon. You'll find that if you go to the door of the temple, it is sealed shut. If you shoot the bird's eye or tail, you will get rupees, but won't unlock the door. Look up at the ceiling and you will discover a pink stone. Shoot that with your slingshot to open the temple door and go into the Skyview Temple.