It just sticks on. But- be careful to line it up just right. Lay it down and see how it fits prior to removing the sticky tape covers. Once it's on, it's on for good, so you want to position it perfectly and evenly. Not as easy at it sounds, as once the guard even touches the bumper, it wants to stick, and stick hard.
I was hoping that the rear bumper guard would form more of a step, but it's tilted at an angle, so the rear bumper isn't very easy to stand on, even after the guard is in place. Also, since the roof racks aren't spread very far apart, and the rear one is quite a bit forward, it's not even that useful for tieing objects onto the roof rack. There's better access to it by standing on a wheel or on the rear door shelf. Frankly- this is one of the things that makes the Tribeca a little less utilitarian for me, but, everything is a compromise. It drives a heck of a lot better than an Explorer or Envoy.