Position the Glacier Bay medicine cabinet on the wall where you want it to hang. Ask a helper to hold it in place while you place a level across the top of the cabinet. Once the cabinet is level, trace the top of the cabinet on the wall with a pencil. Look between the cabinet and wall for the two mounting brackets, and place a mark on the wall at the center of each bracket.
Place the medicine cabinet on the floor and against a wall in a spot that's out of the way. The back of the cabinet should be facing out. Measure from the top of the medicine cabinet to the top of the mounting bracket holes on the back of the cabinet. Transfer the measurements to each of the mounting bracket marks on the wall. These are your pilot-hole locations.
Drill a pilot hole at each location with a drill bit slightly smaller than the plastic anchors that you have purchased. Tap the plastic anchors into the pilot holes until they are flush with the wall.
Screw the retaining screws into the plastic anchors with a Phillips screwdriver until the screw heads are three-eighths of an inch from the wall.
Lift the medicine cabinet up, and position the keyhole slots of the mounting brackets over the screw heads. Gently pull the cabinet down to lock the mounting brackets over the screws.