Prepare the appropriate weight taking account of your fitness level and training type. Squat and grab the barbell using an overhand grip at a little wider than shoulder-width so that elbows are at a 90 degree angle in the lower position. Take a shoulder-width stance and raise the barbell up and behind above head.
From the starting position lower the barbell down behind your head while bending your elbows. In the lower position, go down to the point where your elbows are at a 90-degree angle. Return from that position to the starting position the same way, inhaling while moving to the lower position, and exhaling when you are raise the barg upwards.
Choose the weight taking account of your abilities, overall fitness level and training type. Start using lighter weight to master the technique well. Return to the starting position with a slow, controlled motion rather than quickly relaxing the tension in your muscles. If possible, exercise in front of a mirror and avoid involving thw trapezius muscles. Fix you torso while doing the lifting to avoid bending at your lower back.
Exercise in front of a mirror to make sure your arms are in a symmetrical position and the entire motion is synchronized.