If you scroll up to the comment by Sam 6 and click the more replies button Zest Subject posted a link. That is the xbox 360 branch whereas this is the main group and the meeting point for all the consoles. I'm not sure if there are any other xbox groups because I'm on playstation 4 myself so sorry if I've missed out anything.

Thanks man I'm going to join if I can ha.

No problem, and they should let you in as soon as they see your request. There is no recruitment process as far as I am aware.