I sent you a club invite.

Anyone can send challenges to anyone else. For Daily/Correspondence games, just click on the club member list and click on the Chessboard icon near their username.

Live games seem a little tougher to setup... I think you both have to be in the liveplay section of the site and you have to create a challenge and put in the username. I've only managed to get those going with Csargo so far.