Well, you need the escutcheons (plastic holders) that go into the seat. If you press down firmly on the seat you will feel the tubes that the escutcheons fit into. TBH, I spent a good ten mins making sure I was cutting in the right place. Make a small cut in the seat fabric where you feel the top of the tube. Then, push the escutcheons down, IIRC they require a quarter turn to lock them in. Then, put the headrests into the escutcheon, job done
