Screw removing the control arm nut and all that bs.
I had the same issue on my v2's as your having. Simple solution, take a long flat screwdriver or a screwdriver type pry bar and insert it in between 2 coils on the spring just bellow the bottom of the black thing. Pry down on the pry bar which will jam the black piece up into the body of the car, once you have that done you can easily adjust the purple color. Just make sure the pry bar pivots on the spring coil. So basically the pry bars fulcrum is on the spring coil and the end of the pry bar is in the middle of the bottom of the black thing.
2006 325i 6MT|BC Flushstance Coilovers|Floss BBS Style 5's|Black Kidneys|Alpine Type R|Alcantara Wrapped Sport Wheel|Mtec V3 AE