Built up grime and oxidation 'fogs' up the headlights.
Start with the sand paper pad marked #1. This has the most coarse grit.
Liberally apply the lubricant to the headlight.
Scrub with a good amount of pressure horizontally and vertically. Make sure to cover entire surface. Be very careful not to touch the painted car surface.
As you scrub, a film will become visible. This is essentially all the grime that you are sanding off.
Rinse off the grime.
Repeat the previous steps with pads marked #2 and then with #3. Rinsing each time.
Once finished with pad 3, rinse and dry completely. Now that all the grime is gone, we need to seal the lens surface.
Spray several spots on the light. Don't spray too much, just enough to cover the entire light.
With a microfiber cloth, rub the sealant into the lens.
Voila, looks brand new!