Enter the Wasteland. If it is night-time, play the Sun's Song to see a little bit better. Look for the sand river in front of you, then either fire the Longshot at a crate on the other side, or put on your Hover Boots to cross it. Then follow the flags. Do not visit the Carpet Merchant: he wants to sell you Bombchus for 200 rupees! Keep on following the flags until you reach a small stone building. Climb the slope on the right, then read the panel and use the Lens of Truth. Now, follow the ghostly guide through the wasteland. It is way better to avoid enemies in order to not lose sight of the guide.
After going through the Haunted Wasteland, go right and look at the wall near the two trees. Blow it up on the cracked spot, then get in the Great Fairy's Fountain to receive Nayru's Love. Get out, then go straight ahead, near a dried out oasis. Climb on the rock nearby and play the Song of Storms to fill up the oasis and get a Fairy Fountain. Then head to the temple west on the map. Get in, then get out immediately. Sheik will appear and teach you the Requiem of Spirit. Play the Prelude of Light, turn back as a child, then play the Requiem of Spirit to go back to the Desert Colossus and enter the temple.