Changing a 2005 Honda Civic Taillight Lens (aka: removing your bumper)

Step 3 Step Three: In the wheel-well

The "bumper" wraps around the back of the car up to the rear wheel-well.  Inside the rim, coming up from the bottom, there are three screws (these will also be holding the "mudflap" in place if you have one) you'll need to remove.  Above those is a little notch with a bolt you'll need a rachet to remove (you might be able to get it with a wrench).

Once the screws (and bolt) are out you might give the bumper a little tug to pop it free of the little semi-clip tabs in the lip under the main body of the car.