You did not say if the car is an early or a late model. It makes a little difference - but not much.
The cover is held on with small bolts that go through the body. These are held in place with some lock nuts accessed from under the fender well. You will have to remove the plastic under panel on the left side of the car. There are about five nuts on either side. The best tool to remove them is a deep 8 mm socket and a very long 1/4 drive extension. This will release the sides.
The rubber bumper guards hold the under part of the bumper on. Pull back the rubber cover from the bottom to expose access to the bolts. The bumper guards then just slide out.
The upper center of the bumper cover is held in place by some Phillip's head screws. The older models have a metal strip that pops out. The newer model has small plastic plugs covering the screws.
The older cars the lights are bolted in behind the cover and come off with the cover. The S4 up the light fixtures are removed from inside of the car and should be removed from the bumper cover before removing the cover. The entire unit swings out and detaches.
On the older cover the light fixtures have to be disconnected from inside the car. Remove the tool kit and the last screw holding the rear quarter panels. There is a white barrel connector that unplugs and can be pushed outside of the car for each taillight. As the cover comes off you can disconnect the number plate lights.
Once the cover is off check the aluminum bumper and the supports. The supports are really shock absorbers that have a one time use. They are oil filled and a bump from another car can break the seal and render then worthless. If they are pushed in they are bad. You can tell this often from the bumper cover as it will be pushed in. Pulling the bumper shocks out will change the position of the bumper but takes away the protection that is afforded by properly filled bumper shocks.
Hope this helps.
Dan the Pod Guy