The bar rests on the floor and across your shoulders, not suspended on a bench. Lie on your back with your knees bent, feet flat on the floor, and your back and head flat against it. Unrack the bar and press it straight up. The range is shorter than a bench press because your elbows only drop until your triceps touch the floor. That shortened range shifts heavy work to your triceps and shoulders. The movement is pure pressing strength. Press the bar straight up with control, no bouncing.