You must use M Specs. If you have aftermarket wheels, then you cannot get aligned at the dealership because all BMW stock wheels have holes on the wheels that fit their proprietary alignment machines. Therefore, you must go to a specialist BMW Shop that are able to align aftermarket wheels to M Specs. Do NOT go to a generic shop, ask me how I learned this...
Do not attempt to align your car at home. It will be nearly impossible. Along with the compensation weights needed on the passenger and driver side, you cannot get it as accurate as a shop with the proper machines.
Good luck.