Attach a single grip handle to the cable crossover machine and position it so it is slightly above waist high. You will probably want to use both hands to grasp the handle to position yourself properly.
Once you're positioned correctly, just use one hand. In the correct start position (starting with the left hand) the left hand is gripping the handle with your elbow back behind your body. Your left foot should be behind you and the right foot stretched out in front so you are in a semi-crouched position.
Rest your weight on the leg behind you. Your right arm should be pointing straight out in front of you. Now push the cable out in front of you until your arm is fully extended, twisting your torso and shifting your weight to the other leg. Pause for a one-count, return to the starting position and repeat. In the finish position, the hand holding the cable should be fully extended in front of your body and the other arm should be behind you. After completing 10-15 repetitions, switch to the other arm.