How do you get on an island in Endless Ocean Blue World

An Island, are you refering Nineball Island, or islands you can go ashore?
In other cases, I'll just answer both above: further the plot on the game for Nineball Island
Going ashore: Just find an island you can go ashore(If not sure, use the map; ashore places are colored purple) Surface, then an option will appear "go ashore"
Click on it, and have fun
(Note: I recommend doing Chapter 3 Arctic Ocean it shows good tutorials)