Your options if the power window is not working are:
* Troubleshoot the electrical system: Check the fuse, wiring, and the motor itself. A simple fuse replacement might be all that's needed.
* Use a temporary fix (not recommended): Some people have rigged up solutions using a strong suction cup or strategically placed straps to hold the window partially closed, but this is very insecure and should only be considered a temporary, emergency measure. It's unlikely to be effective against wind or rain and could damage your window or vehicle.
* Get it repaired: The best solution is to have the power window motor or related components repaired or replaced by a qualified mechanic.
In short, there's no manual override for the rear window on a 1986 Ford Bronco.