It may sound stupid, but there is no uninstall button, how am I supposed to uninstall this game?

1. This should go in computer or gaming chat (?)
2. What game?

You don't, you delete the files directly.

just delete the folder and you should be set

Start -> My Computer -> Local Disc (C) -> Games -> Delete Toribash-3.* Folder

Unless you changed the directory 8/