Grab a barbell, load some weight on it and set it down in front of you.
Stand with your feet at around shoulder width, bend at the knees, and squat down to grip the bar with and overhand grip (thumbs at the bottom) and your hands wider than shoulder width apart.
Keeping your back straight, stand straight up so you're holding the bar in front of you against your waist.
To get into the starting position bend your knees slightly, and while keeping your back straight let the barbell slide down your thighs until it drops just below knee level. This is the stance that should not change throughout the set.
Now pull the bar up to just below your chest.
Squeeze your shoulder blades together at the top of the movement.
Then slowly lower back to the start position.
Repeat for desired reps.