I installed the rear fender assembly that includes the rear turn signals, tail light and brake light housing, the fender, mud flap and license plate bracket with side reflectors. This is easy work if you remove the rear wheel. But, there is a lot of hardware used and I show what goes where.
This is a link to the detailed documentation and a short video summarizing the work.
VIDEO: 1983 BMW R100RS Install Rear Fender And Lights
Here are some pictures of the work.