Take a stance with your feet shoulder-width apart. Grab the pulley bar with both handsusing an overhand grip. Step back from the pulley, slightly bend forward and bend your arms at the elbows at about 80 degrees. Hold your elbows close to your torso.
From the starting position do the extension (contracting the triceps), arms stretchingto along your thighs. Wrists are firms throughout the entire motion. Go back to the starting position and inhale. Exhale doing the extension. Your torso stays in the same position throughout the motion. Do the required number of repetitions.
Keep your torso firm, do not bend at waist. Elbows stay in a fixed position, not moving sideways throughout the entire motion.
Choose an appropriate resistance to start with to master the technique well. If possible, exercise in front of a mirror to get the correct starting position and watch the entire motion.