Remove the reflector, then remove the trim piece. There are several pieces which both hold the bumper in position and allow you to adjust it in and out. Pull out #10 and the o-ring. Then you can turn #8 (there are two notches in it) using some needle nose pliers. When the bumper is lined up the way you want pop #10 back in and turn to lock in place.
Parts 8,9 & 10 in this diagram from realoem: