pop your trunk.
under the trunk handle you will see 4 screws. (two on the outside, two on the inside)
unscrew these. (the screwdriver in your toolkit will work for this!)
pull off the trunk handle.
slide and pull the blown bulb out.
put in the new bulb securely.
turn on your lights, make sure it works fine and try rattling the bulb holder to make sure it's secure. (and there isn't a short in the wire! ... E36's are known for having flickering license plate bulbs when going over bumps.. hence why they blow so quickly!).
All looks good? ... Turn the lights off... snap the holder back in place and screw the trunk handle back on.
* Do not put in the bulb while the lights are on... chance you could cause a power spike and blow a fuse.