The proper way to wear a backpack is with the bulk of the bag sitting two inches below your shoulders. Ideally, a backpack should end at your waist level and never sit less than two inches above your hips.
You can adjust how a backpack sits on your back by tightening and loosening the straps. Ensure that the pack is flush against your back and that the waist and chest straps are tight so that the weight of the bag is evenly distributed.