Select a resolution from the list. Make sure you know your computer's limitations when you select this.
If you want the game to run in a window (instead of running full screen), select "Windowed".
The shadow will be low resolution by default. If you machine is faster than 1 GHz and you have more than 32 megabytes of video memory, you can safely select "Hi-res Shadows".
If you created the game, make sure your opponent has selected the options te wants.
After both players are ready, the creator (or host) can press "Start Game"!
The host will start the game and will be the blue player.