First you do a quick registraton. It's best if the username you choose is the same as your Gamertag to avoid confusion. Next click on the[i] Forum[/i] section (in the green menu-bar at the top). There should be a section called "[i]Looking to join?[/i]". Click that. It should have a simple sample to show you the kind of info they need (like your Gmaer tag and stuff). Its kinda convoluted, but I like that it's organised.