In the stem of the headrest you fill find a grove. I have used both a thin piece of sheet metal in the past and today, at the yards, I used the top of an antenna which I cut off with some wire cutters, (Hey! I was at the yards! Ya work with what ya' got!!!) anyway,.... pull the headrest about half way up and slip the sheet metal (or antenna stalk) into the groove about 10"-12" inches and slide the whole headrest out of the seat.
There is a stop that rides against the stem. It is spring loaded. It must be held away from the bottom stem. The sheet metal ( or antenna) creates a ramp for the spring loaded stop and the headrest will come out.
I was told that you could reach up inside the seat upholstery from the bottom, but I have had no success with this.
Art