Through the rubber cover

The following is the method I used on the left side after trying the right side by using the hard cover (described after this procedure). This is SO much easier to install and route wires, however, you MUST make sure you seal the gasket to the rubber boot so as to keep water out. I personally think this is the best way to do it with the kit I used.

I used a scrap piece of cardboard, cut in a 7/8" diameter circle, and traced the back side of the low beam rubber cover using a permanent marker.