Path to menu: Main menu - Challenge
From here you can challenge other players or the computer. Avatar opponents need to be nearby the board to get listed in the menu.
Select a name to challenge a player for a match. He / she will get a dialog, asking to confirm to start a match with you. The other player can deny or ignore your request.
When a match is started, white and black is randomly assigned unless your opponent selects a certain color.
You should have verified or set the clock in advance. You can adjust the clock until white plays a move.
To play a match against the AI engine, select 'Computer'. From there you can play a skirmish match or customize an AI engine.