Remove the upper drawers. Then clamp the bottom panel into place on the drawer, so all the edges line up with the cabinet. Use a counter sink drill bit to pre-drill screw holes through the drawer into the panel. The counter sink bit creates a space for the screw head to sit as it drills. Drill four screw holes for a deep drawer, two holes if it's shallow. Screw the panel into place, leaving the screws slightly loose in case you need to adjust them