The guy at Klassic Komix wants you to find the pieces of a comic strip. He will give you the top and frame, and you have to find the other 8 pieces scattered about the island. When you assemble them within the frame, you will see Nate's locker combination written across the middle. If you show the comic to the guy when you are through, he will give you some gum as a reward.
First, you put the comic strip together. Then you put it with the title piece and give it back to the man who gave you the title piece.
On the powerline
All that you have to do is jump.
on top of the telephone pole
on the way top
The bird does not have a piece of the comic. (see related question)
This is given to you by the guy at Klassic Komix, the same guy you're going to return them to when they are assembled. (For the 8 piece locations, see the related question.)
The piece is on top of the "solar system" display at the far left.
Put together all the comic strip pieces. Give it to the guy who gave you the title piece. Go to the school and chew the gum that he gave you.
You do not play as Big Nate. He accompanies you around most of the island, and races you on the jet skis.
You can't play "as" Nate, but everywhere you go on the island, he tags along.
There is no Duke among the characters of Big Nate island.