If you are starting a new game you wont be able to visit Storm Island until after you unlock the first Car Meet. This happens after you finish your 2nd Championship Event (which will be in Niece).
After a brief intro video to Storm Island a new icon will appear in the harbor area of Niece. Just travel up to it, press
(or
) and you will be transported across to Storm Island.
You will be then automatically be put into a Ford Ranger and told to travel to the Festival Services Center. Complete this and the achievement will unlock.