Come into a standing position. Your feet are hip width apart. Pelves tilted slightly forward, avoid a hollow back. Grab the resistance band behind your back. The wrist of the lower arm is facing away from you, the wrist of the upper arm is facing towards you. The band is already under tensions. Straighten the upper arm. Elbows stay at the same position and close to your face. The movement comes only from the forearm.
Bring your resistance band under tension behind your shoulders. Arms are stretched to the sides. Bring your straight arms together in front of your chest.