Sorry for delay in reply - been a looooooooong day/night.
What i'll call the inner edges of the bumper (closest to car) - snaplock over the rebar. From memory - you just have to kinda lip the edge up along the bottom first - then top edge will pop off easier.
If you start at top side first - its way more battle.
From memory, and its been couple years.
If you get up under there with a good flashlight at dusk or dark - you'll be able to see better about how/where it snaps-unsnaps at.