lift the hood first
then find the phillips head screw for both parking lenses, and remove the one you need.
I use a thin blade flat tip screwdriver to get some leverage behind the lens. Pull firmly but there is nothing really to hold onto. Use your left hand to pull straight forward on the lens while your right hand applies some pressure from the back and the rear of the lens.
Once it is out you'll see better how it fits into place and the 2nd time you ever have to do this will be a piece of cake.
jamess is describing it properly as well but if you have "fat fingers" this is a tough one to do the first time. Be patient and try to pull evenly along the back side and the underside of the lens....