On the status page is a list of games it's your turn to move in. A click on the game number will display the game.
 
When viewing a game, a stone is placed (and a move is made) by clicking on an empty intersection. If this move kills any enemy stones, they get automatically removed by the server. For passing or resigning, follow the links below the board.
 
When the game is refreshed with the new stone / pass / resign, press one of the submit buttons to confirm your choice. If you change your mind, press the go back button.