check the threads on this site, think I read somewhere that the lugs for it to drop onto are screwed onto the back door, so the seller perhaps should have given you these too. Been through RAVE, but couldn't find the instructions for this part no: STC53047, but I have definitely seen it somewhere in one of the forums, 'cos I checked before I bought one, so best get searching ! (apparently there are other forums available, but I wouldn't recommend it)