How do I clean the inside of my Ford Focus headlights?

There is a film (of dirt?) covering the plastic on my 2000 Ford Focus headlights. How do I remove the headlight or lens cap to clean it?|||Only way to have dirt and crud on the inside of the headlight is if it is cracked and broken and dirt is getting inside. Usually the plastic gets a "milky" or smokey tint to it that can most times be restored or removed by putting a good coating of rainx on the headlight outside and rubbing well. It is amazing how well this works on some that are almost no longer transparent. Try it if you get a chance.|||I just read that the plastic gets cloudy and you can't clean it . If u still r under warranty bring it back.. If u get stopped and they check the light coming out of it and it's not to specs,you get a citation. How about that.|||they should have screws or some sort of plastic clip on them