you'll need to remove the rear seats, if its an early car they are a one piece unit, the later ones have folding back rests and are in two halves. remove the rear roof trim then the rear upper sections of the trim panels having un screwed the locking buttons and seat belt mounting on the top. then you should be able to pull the lower sections of the trim panels off. to get the lower sections out of the car you'll need to unbolt the full seat belt assembly.you can do it with the seats in but if you've not stripped on down before it might be best to take them out, plus it gives you more room to work.
enjoy its an alpine