Just click on the number to add an X mark. At the top you can see team 1 and team 2. Click on it to change to Player 1 and Player 2. You can erase X marks by draging the eraser across. (HINT: don't move mouse to fast when using eraser.) Change the score by pressing the 'change score' button. It's the best way of keeping score Enjoy!!!
Please comment if there is a problem!