Hello Ray.
If this is the one I am thinking of it is a small black cover for the door handle. It actually slides on. You have to slide it to lock it into place from the left to the right. You will need to put some tension on it by pressing it in slightly as you slide to get a good lock. It will often pop off it is not quite right. It can take a few tries to get it on good. If you still have trouble most dealerships (if you stop by at a time it is not busy) will be able to pop it on for you. ( Most of the time they will not charge for this.)
I hope this helps you getting that piece on! Let me know if I can help you further. Thank you.
BMW Mechanic
Level 1 BMW Master Certification, 9 Years Dealer experience, Team Leader, Shop Foreman