Man, I really don't know what to say. If you can't figure out either what the jump key defaults to or how to change it to what you want, you really may be the stupidest person on the internet. Here are three seperate methods you could have used to discover the answer on your own:
1. Read the f*cking manual. This is probably the best answer, since it will probably teach you stuff on how the game plays as well, answering your next question: "How do I spin dash?"
2. Go into the options and find where to configure the controls. For your information, it's the very FIRST option on the list, so I'd better not hear anything about "WHERE IS IT?"
3. Press every damn key on the keyboard. This is slow and boring, but it sure as hell works. A lot better than asking a dumb question like this on a message board, too, since you won't get the entire place laughing at you.
Now if you'll excuse me, I'm going to go cry about the future of the human race.