This is an excellent exercise to allow you practice the correct technique for the squat. To begin, grip in front onto a solid structure such as a stair rail.
Like a traditional squat, have an erect spine, with a natural arch in the lower back. Have your feet in a comfortable position, between hip and shoulder width apart. You may find it more comfortable to have your feet slightly turned out.
As you squat down try to maintain your trunk in a line parallel with your shin bones, whilst keeping your knees aligned with your feet – use the support in front to help maintain correct alignment.