Assuming this is your first time through Sumemrfalls pass this guide should get you going:
SUMMERFALLS PASS
Dive under the water and collect the Melodia Idol. Head to the left and leave the water. Jump onto the platform to the right and use the torch to burn the sapling. This will create a Seed. Carry to the Seed over to the left and plant in it in the earth on the small platform. This will create another Sapling.
Water the sapling using a Slipstream and it will grow into a Poyak. Use the Poyak to reach the ledge with the lever on it. Pull the lever to open a door under the water. Go down here and collect the Melodia Idol from behind the door.
Emerge from the water on the left. There are a couple of Fire Glorbs here. Gust them into the water, before pulling the nearby lever. This will open a door behind the waterfall above. Go back to the start of the area and use Sonté’s Shrine to make it Winter. Break the frozen waterfall with the nearby torch and leave to the left.
Michael