To begin, place the bar in either the high bar or low bar position. High bar is with the bar resting across the traps. The low bar position is when the bar is resting across the rear delts.
To begin, breathe and brace your abdominals as you lower into the squat breaking at the hips and knees at the same time.
As your butt touches the box keep your core braced. Do not relax your body. Once you are on the box, come to a dead stop.
Stand back up exploding while keeping your core tight. Drive through your feet, and finish the movement by locking your hips out at the top.