the leading edge has a metal bracket that fits in there and attaches to the bumper cover. there is one screw to attach it to the wheelwell edge of the fender, and a couple small studs on the backside of the top edge go through the fender with nuts on holding it on.
if i didn't just put them on, i'd take a pic for ya. but like quick91lx said, there's a bracket on the front bumper with 2 studs that stick through 2 holes in the extension which attach it to the front bumper, and 3 studs at the very top of the extension that go through the fender.