i bought the car used and everything works except i can't open the passenger side rear door how do i get the cover off so i can try to fix it

From the inside or outside?

Do you have child locks on the rear doors (very common) and is that one engaged?

i can't get it open from the inside or outside.

still can't open the door.

You need to pull the seat and pull the panel off the door and see what is going on. If the latch is internaly broken, the latch will probably need to be drilled. It would probably be best to take this to a mechanic if you can't see an obvious problem when you pull the panel off.

how do i pull the panal off when the door is closed.

You'll need to pull the seat. Then you should be able to carefully pry the door panel off.