Ahhh, the lost forgotten art of aiming headlights
Most people don't bother because many state inspection centers no longer check this. This procedure applies to any car, and not specific to an E36.
If you wanna be really anal about it, check your tire pressures, have 3/4 tank full of gas, and add the driver's weight to the driver's seat. A flat level surface with a perpendicular wall is of course required. Pull as close to the wall as possible, and mark or tape a horizontal line across the hotspots of your low beams. Then mark the vertical lines. Your marks should then look like this:
Alternatively and more accurately, you can measure the distance from the center of the low beam bulbs to the ground, and transfer that measurement to the wall, and mark your verticals dead ahead of the bulbs. But it's not necessary unless your lights are really whacked and you're lighting up rooftops as you drive by
Back up to 25ft from the wall and adjust the low beams so that the hotspots are 2" down and 2" to the right of the wall marks. Just for reference, the high beams should be about the same height, but centered 3" in from either vertical mark. But this doesn't apply to your E36, since the adjustment is at the housing, not on the individual lights.
Now for the reality check: the hotspots obviously get bigger as you back away, so how the hell do you measure 2 or 3 inches?! Just move the lights a smidge in the said direction