Prepare the appropriate weight matching your fitness level. Grab the barbell using an overhandgrip at shoulder-width, lie down on a horizontal bench and move the barbell above your chest, holdingit with your arms outstretched.
From the starting position lower your stretched arms with the barbell behind your head until it is horizontal with your body. Inhale while moving the barbell behind your head and exhale while going back to the starting position. Do the required number of repetitions.
Watch for the correct starting position of your arms. Watch for dorsal flexion of wrists when moving the barbell. The torso must remain firm without bending at the waist (lumbodorsal swayback), especially when you move the barbell back and down.
Choose the appropriate weight taking account of your fitness level and coordination abilities; that means doing the motion using a lighter weight to start.