På eller i

Hi, I just need a quick clarification. I have a book I am using to learn Norwegian, and I was talking with a Norwegian dude whom I know. It says in the book that på is used when saying you live on an island, for instance, 'jeg bor på Skye.'

I was talking with him, and I assumed the same would apply from where I come from, the UK, but he told me that I was supposed to use I instead of på and now I am royally confused about it.

Could someone clarify for me? cheers