The hack squat machine targets the quadriceps femoris (quads), and gluteus maximus, gluteus medius, and the gluteus minimus (glutes) primarily, with also some focus on the hamstrings.
First, find a foot position that is comfortable and safe for you. You knees should be in line with your toes. As you lower you should also make sure you back does not round.
To start, place your shoulders underneath the pads, grip the handles on either side and bring them inwards towards your head to unlock. Push upwards to lift. Make sure your knees do not lock and slowly move downwards making sure your heels do not come away from the platform. Once finished make sure you lock the handles back into their original position by moving them outwards and you can then step off.