Run ahead, along the path, and you’ll soon encounter a Sheikah Stone (ahh… Ocarina of Time has influences even now). Just watch the scene; it is fairly self-explanatory.
After the scene, go along the path and back to the Bird Statue. Use it if you want to, then go through the gate and downstairs. At the bottom. go left and along the wooden boards to find the waterfall. Hop across the rocks (be careful about falling - you will fall, albeit unhurt) to the other side. There, go up the incline to the waterfall entrance. Cut down the blockade and walk inside.