After learning the Song of the Hero, go to Skyloft and play the song near the butterflies near the Light Tower to open the Goddess's Silent Realm.
Collecting the Goddess's Tears
Collect Tear #1 straight ahead, near the Guardian Statue.
Turn around and climb up the Light Tower, avoiding the Watcher that circles around the upper level. At the top, find Tear #2.
Go up to the bazaar area and get Tear #3 from in front of the Guardian statue.
Carefully avoid the Watcher that floats around to get Tear #4 nearby.
Go to the east side of the bazaar and get Tear #5 under the tree.
Jump down to the lower area and avoid the Watcher to cross the stone bridge to the residential area. Get Tear #6 on the other side of the bridge.
Turn right and go to the graveyard, being careful to avoid the Watcher that floats there. Get Tear #7 from the far end of the graveyard.
Carefully avoid the Watcher again to get out of the graveyard. Head north and then go east under the land bridge to get Tear #8.
Go back under the land bridge and head north to where four Watchers are floating around a tear. Wait for there to be a gap between their lights and run to Tear #9 in the middle. Wait for another gap to appear between their lights to run out of their area.
Go back across the stone bridge, avoiding the Watcher. Head north to the stepping stones in the water. Get Tear #10 just before the stepping stones.
Go across the stepping stones to get Tear #11 on the other side. Go back across the stepping stones.
Go west along the wooden bridge and carefully avoid the Watcher to reach Tear #12 on a narrow piece of wood.
While avoiding the Watcher, go west. After crossing a short wooden bridge, turn left when you see the stairs on the right. Go up the stairs on the left and go to the stairs going north. Get Tear #13 at the top.
Go between the fences in front of the Knight Academy entrance and carefully pull the wooden crate back, letting go to run away from the Watcher's light when it comes near. Once you have pulled the crate back enough, stand on it (walk toward it until you climb up) and get Tear #14.
Finally, go to the left of the left side fence and run up the wall of the academy to grab onto the wooden ledge. Go left and then jump off on the awning. Jump to the second awning and climb up the vines to reach the roof. Get Tear #15, then carefully make your way back to the entrance of the silent realm, avoiding Watchers and Waking Water.
You will receive the Stone of Trials.
Opening Sky Keep
Go to the stone state of a bird near the stepping stones on the north side of the lake. Examine the statue to put the Stone of Trials in place of the missing eye. A structure under the Goddess Statue will appear, and some floating clawshot targets will appear. Use them to get into Sky Keep.