Can I join more than one leaderboard group?
To join additional groups, go into the app settings (top left corner of the app) and select groups. Then type in a group code (a current group member can give this to you) then select Join Group.
To view other leaderboards, go to your leaderboard screen and click the down arrow next to the current leaderboard group name at the top of the screen. That will show you a list of all of the groups you have joined.