The Whole Community is using mIRC or Hexchat (or any similar Programm) its a chat programm where u can join some channels to play 7on7 or 3on3 games.
At Hexchat: you just need to download it put your name in it, The network is always Quakenet and right after you click connect.

Channels which are important:
to join a channel write /join #channel

so several channels are:

#ios.mix (mix channel to play 7on7)
#ios.street (street channel to play 3on3)
#ios.dev (for ios updates)
#ios.league (official league channel to get news from iosleague)
#cubs.priv (the Cubs Group to organize Matches)

on the top there is always a Topic, you can easily write your name infront of the Position you would like to play !!!


Any more Questions just ask $imu