Attach the band so it is fixed medially to the position of your arm (so you will promote resisted external rotation). Set shoulder blade into neutral and maintain elbow position at a 90 degree bend. Use your opposite arm to assist with lifting the exercising arm infront of your body until your elbow reaches shoulder height. Let go of the exercising arm, and slowly lower it back down to the start position, ensuring the elbow stays bent at 90 degrees, resisting the band tension by not letting the band pull your hand inwards so you are staying in 0 degrees external rotation until the elbow reaches the side of your body. Repeat.