In a standing position, place the ball should height against a flat surface such as a wall.
Place your forearms and palms flat against the ball. Lean on it with your body weight. Keep your back flat and feet flat on the floor.
Push yourself back away from the ball with your hands extending your arms. Contract your triceps, pause and lower back down to starting position. Repeat.
This is also very similar to a regular push-up exercise, however you are placing your hands closer together so that you will concentrate more on your triceps rather than your chest muscles.