How do I get the rear right passenger door open light to go off.

Hello, there is a door switch either on the door or within the door latch that will communicate that a door is seen to be open or closed. If they are not working properly, it can show a door to be open when it's actually shut. If it shows to be open, the warning light will be on and it will be impossible to lock the door. Try using some lubricant spray, like WD-40 for example, in the door latches and if you find a door switch on the door, there also. Open and close the door several times to see if the issue resolves.