This movement is performed in a standing position. Preferably by a squat rack to make it easier to grab the barbell and lower it safely down again once done.
Stand with your knees slightly bent. Grasp the barbell shoulder width, be sure to get a firm grip with palms facing in. You may use wrist straps to relieve forearm strain if you use a heavy weight.
Now, raise the barbell from its support and raise your shoulders as high as you can keeping your arms close to your sides without bending at your elbow.
Hold for 1-2 seconds, contracting the muscle. Then release back down to the starting position.
This is an excellent movement for training your trapezius muscles. The key in this exercise is to let your trapezius raise your shoulder, without jerking it up.