Took me about 30 minutes to do, and that was with the car on the ground. It would probably be easier if it were jacked up some and on jack stands...
Tools and Materials:
10mm Socket and Ratchet
Pointy Screwdriver (Or drill)
3M Outdoor double sided tape
Garage Door Bottom (I got it in a 12 foot roll. Only need about 7-8 feet)
First, you'll need to remove the radiator guard under the car. You can do this by taking out the 5 bolts pictured below.
Once you have that off, lay out the Garage Door Bottom along the bumper on the ground.
Next, stick it onto the bottom of the bumper. I found out that once you stick it on the bumper, it doesn't like to be taken back off. So get it right the first time :p