How do you get spider man costume in Homer Simpson saw game?

There is no "Homer Simpson Saw Game". It is likely you are thinking of a different game, possibly a fan-made mod or a game with a similar premise.

Could you please provide more information about the game you are referring to? For example:

* The name of the game: Is it a mod for a specific game?

* Platform: What system is the game on (PC, PlayStation, etc.)?

* Any other details about the game: Is it a horror game? Is it based on the "Saw" movie series?

Once I have more information, I can try to help you find out how to get a Spider-Man costume.