Drill a hole through the middle of your PVC cap. We used a 1" spade bit (a hole saw will work as well) to accommodate all of our wires. Bundle all of your wires together and compare to your bit before you drill.
Our cap had raised writing on the center of the cap. You can sand this off with sand paper. It isn't a bad idea to give the entire cap a light sanding with a fine grit sandpaper. It will help you paint stick. Paint whatever color you desire.
If the cap is too deep for your liking, you can cut it down. We took off about an inch. I recommend carefully using a handsaw or coping saw. If you want to do it quickly with a miter saw create a jig to hold it securely in place.
Next you will need to drill two smaller holes to connect your PVC housing to the mounting plate. Be sure figure out which holes you will use to connect your plate to the junction box and then decide which two holes you will use to connect the PVC housing. Make your holes large enough to accommodate 3" machine screws that fit your mounting plate.