Hope this helps. If you look real close you can see the metal release latch poking out. Take a flat head and push it down. Once depressed you should be able to pull the headrest out.
Nice job so far by the way, remember to get everything nice and tight. Also, be sure to tighten down those three cloth "rings" that are on the bottom of the seat. If you don't do that your rear seam will work itself loose over time.
