1993 Ford Explorer 4 Door
All doors will open with the switch on the drivers side. All will lock back except the right front one.
Any ideas and can I fix this myself ?

It sounds like the door lock actuator for the RF door has gone weak. The job requires a driller to drill out the old rivets and a rivet gun to install( or you can try to use screw and nut, but sometimes it's hard to put on)