Also known as the 45 degree back rise, the Hyperextension works on your hip hinge which includes your glutes and hamstrings.
First adjust the pad so that the top of pad is in your hip crease or just below - so that you can hinge over the top.
Once in position ensure your feet are also secured. Make sure you have a neutral spine by ensuring your chin is tucked down. Then focus on lowering yourself by throwing your glutes behind you. Going nice and flat making sure you have a deep stretch in your hamstring. To push back up, use your glutes against the pad. When going back up make sure you don't over extend upwards.