how can i get to the fuse box, located under the rear seat of a 1988 bmw i735 il?

well i got the car like six months back, but when i got it of my friend, he upgraded from the original cassete receiver to a aftermarket cd player. He told me that the stereo worked but for some reason the speakers did not produce eny sound,(the stereo turns on, but no sound). I took the car to stereo shop, they checked it out, and they told me the car needed new speaker rewiring. I took the car back home becouse i did not believe the car needed that, i started reading the owners manual, and discovered that the car had a 2nd fuse box located under the left side of the rear seat. bBut i been trying to get to the fuse box without damaging the electric motor that pull the seat back and foward.