How do I perform a seated shoulder fly with both arms?

Sit on a bench with your feet pointed straight ahead and your feet placed flat on the ground.  draw-in your navel and hold a dumbbell in each hand, with your arms hanging at your sides.  Raise both your arms up and away from the sides of your body with your palms facing down.  Raise the dumbbells to shoulder level being careful not to shrug your shoulders or arch your back.  Hold the top position and then return your arms to the sides of your body.