This might not be the best place to ask this but I kind of need some help and was hoping someone might be able to.

I have 2003 focus hatchback. Well I have a tail light out. and I bought the bulbs and and everything. but i cant get the damn casing off the light. I only see one screw on the side and then it just wont budge. any suggestions as to what I am supposed to do to get the tail light cover off?