Unfortunately Bentley's photos on this one don't help much. I did this same repair on the driver's door. Here's a link with some tips. Should be intuitive if you have a small flashlight and a dental mirror, and can study it long enough. Access is confined. Use long narrow needlenose pliars or a hemostat, and a long slender screwdriver to work it back into place. If the plastic insert is missing, look for it down in the bottom of the door.