In the online Pong game the movement of your paddle works in exactly the same way as the arcade classic. All you need to do is to be able to slide the paddle either up or down in order for you to hit it back to your opponent.
To slide your paddle up you prees the Q and to slide it down you press the A.
In order for you to beat the computer you need to get used to the angles at which the ball travels when it hits objects. It takes a little while to get used to the way it bounces of the sides and the paddle.
If you get used to anticipating the movements of the ball in the online Pong game, you will be able to beat the computer.