This move primarily targets the shoulders and arms, including:

Remember, this is like a shoulder press but with a rotation.

Sit or stand with feet hip-width apart.
Bring your weights up to collar bone height, with the weights pointing horizontally (bulky ends pointing out at the sides, not in front). Your palms should be facing your body. Brace as you lift and as you do so, start to rotate the weights so that your palms now face out from you.
Straighten out the arms to lift the dumbbells directly over your shoulders.
Come back down, rotating back the way you came so that you end with your palms facing you.

Sculpt shapely shoulders with an Arnold press