You can't play "as" Nate, but everywhere you go on the island, he tags along.
You do not play as Big Nate. He accompanies you around most of the island, and races you on the jet skis.
First you need the keys to the ski jet. Go up the lighthouse to the painter and ask him to see through his telescope. Look through and use your mouse to go right and up. You will see a paper wedged...
'-' :-) ;/ ;D ;l ;-> :] ;0 peace
OYSTER is the answer, if you are talking about hangman.