what consul mate?
It's a pretty easy process, what kind of multiplayer game do you want to make?
Do you mean how do you make a team/gang?
If you simply want to play in a MP match then it's straight forward Main Menu, Multiplayer, Quick Match, wait for the matchmaking screen to count you in, you are on the blue team unless you are gangsta brawlin then everyone is an enemy...
Be a bit more specific about what you want to do in MP and I'll talk you through it 8-)