Tinting your headlights does decrease the performance slightly, but I don’t do too much night driving so decided it was a worthy sacrifice as I really like the way they look.
1. First off pop the bonnet to access the light
2. Get some glass or window cleaner and scrub those bad boys till they are nice and spotless.
3. Remove the indicator. It makes it easier to get at the headlight and the indicator is much easier to do off the van.
4. Cut a piece of film to the right size, allowing to go around all 4 edges of the light. Then peel off the backing and present the film to the light. Starting in the middle press the film down onto the light.
5. When you start going around the curves it gets a little less easy. You will need a credit card or something similar and a hairdryer to help. Use the credit card to slide down the film and push it onto the light. The hairdryer will warm up the film and make it much more flexible and easier to mold around the curves and contours of the light. 
6. When you have finished, give the film a final blast with the hairdryer to ‘set’ it.
7. There you are, your van should now have awesome, mean looking headlights.