Position the bar across your traps, gripping it at just wider than shoulder width, then set your feet approximately shoulder width apart, pointing them slightly outwards.
Start by bending your knees until they are at roughly a 90 degree angle then push through the heels and squeeze your glutes to extend back up to the starting position. Engage your core to keep your back straight whilst pushing the hips slightly back on the way down and then thrust them forward on the way back up. Your knees should bend in line with the angle of your feet. Repeat for the desired amount of repetitions.
Perform the movement at a controlled pace and avoid having your knees cave inwards past your big toes when at the bottom of the movement.