The player that created a multi-player-game is referred to as game-master. Right after creation of a multi-player-game it is in setup-mode, in which the game-master has to find other players, arrange the players into teams and configure the game-settings (handicap & komi). After those steps the game can be started switching into playing-mode. For each multi-player-game there is the so-called game-players page, that provide functions for these tasks, allowing to communicate with the other players and showing information about the participating players.
Start to play the game. For participating players there's a link "Check game" instead of "Start game" (which is for the game-master only), which checks what steps are still missing to be able to start the game. This is just for information, the game-master sees this as well.