Stand with your back to a cable machine, with the machine pulley set all the way up.
Grab the handle with one hand and place yourself sufficiently far for the cable to be under tension when your arm is fully extended behind you.
While keeping your arm straight, push the handle down to bring your hand by your hips, then continue the circular motion forward and bring your hand up overhead, then back towards to the starting position.
Also perform the movement in the other direction. Either direction counts as one repetition.