How do you get multi player on sonic riders zero gravity

If you are a beginner, do not look below these text. All you do is go to servival and pick a challenge to go to, pick a stage and pick a character(s). IF YOU ARE ADVANCE, I'LL TELL YOU BUT IF I FIND ONE MORE OF THIS QUESTION, I"LL ATTACK THAT PERSON! I TIERD OF FINDING THESE QUESTIONS!!!!! READ THE TEXT ABOVE!!!!!! Sorry, anger issuses. just, go play video games and whatever you guys do. I don't know. Note:I'm a boy not a girl, I said that because I don't know you.