Just land on the isle and go into the tower - the bridge is already made. Inside, go forward to the circular design and stand on it. Again, use a Skyward Strike to hit the crest across the gap. Afterwards, a scene ensues and you’ll learn the fourth of the harp songs, Din’s Power.
Our next destination is Eldin Volcano. Exit the tower and dive off of the island, then proceed southeast to exit the Thunderhead. Fly east to the red beam of light, and descend within it.