Click on 'Single Player' to play against the computer, click on 'Multiplayer' to play with a friend on this account, and change the look of your page by selecting a theme. The game is played on a grid that's 3 squares by 3 squares.
You are X, the computer/other player is O. Players take turns putting their marks in empty squares.
The first player to get 3 of her marks in a row (up, down, across, or diagonally) is the winner.
When all 9 squares are full, the game is over. If no player has 3 marks in a row, the game ends in a tie.