Just run UniBall.exe to launch the game.  At the login screen,
if you already have an account, enter your username and password,
then hit "connect to server". If not, just enter the username and
password that you want, and it will automatically create a new
account for you, if that name has not already been taken.

After you have connected, you will see a list of games that are
currently running.  If there are none, or you want to create a new
one, just hit the "Create new game" button, or select one of the
other games, and hit "join game" to enter it. While in the game, hit
F1 for a list of all controls in the game.