how do u find second island code?

[Goblin]

we went to da first one how do i get code for second 1??

[lpnlizard27]

you must make your way all the way to the top, and there will be a whiteboard with the code on it and some other notes.

[Buzzard]

You'll always find the code for the next location *somewhere* on the site. When you do find it, the journal you carry will get updated with the new numbers automatically.

And as the lpnlizard mentioned above, you'll need to get to the absolute top room of the radio tower. Yes, it's up there a good ways. No, fall damage won't quite kill you if you're reasonably healthy before. Landing in the water will prevent fall damage, but... shark.

[Siestalavista]

When you collect all notes, you have the code for next station, this also means that you got an achievement "... historian". After you got that, press T, and now you can see the codes if you didn't notice at the first time you get them.