Below the board, there are buttons controlling the game.
Initially, there is a 'glider' on the board. Click Play to see what will happen.
You can also modify the state of any cell on the board anytime. To do so, click the Pause button. Next, click any cell on the board to handle its state or press the mouse key, hold it, and move the cursor on the board to modify many cells at once. Then, click Play.