Wait until you are standing at the approach to the lane with the ball held in front of you.  Move your player left and right with the mouse.  Press and hold the left mouse button.  Move the mouse in a gentle upward motion, releasing the button along the way.  With this motion you control the angle and force of your throw.

Moving the mouse left or right while the ball is traveling down the lane will add spin to your ball.  Start the ball slightly off center and move or hook the ball into the pocket.

Traditional bowling scoring is used.  You can bring up the scorecard while either player is at the approach by pressing the SPACE Bar.  The current fram for the player who is "Up" is highlighted in yellow on the scorecard.  You can remove the scorecard by pressing the SPACE again, or by simply clicking on the screen with the mouse.