I started by heating up the cover in my clothes dryer on hot for 6-7 mins.
Then i layed it out and stuck the headrest in, front side first
I pulled it down until the front corners could fold inward an even ammount on each side
Then i stapled it in place
Now using your fingers, push the vinyl up the front face of the headrest, this will create a ripple in the cover, keep pushing it toward the rear edge.
Do that several times and you will have made the front taut, and will ahve given yourself the material you need for the back side.
Once i had the back side with enough material to fold the corners over and i was sure it was tight front to back, i stapled the rear edge
Then it was time to work the sides... I pushed them and sliced the cover so it could wrap around the post
Pulled it in and tight and stapled it UNDER the front flap.
The rear corners were where i struggled. WIth that foam sewn onto the inside seams, it made it real thick and hard to fold over. This was the best i got on this side. Luckily this is all invisible once the headrest is on.
The other corner looks uglier, but it actually came out better & flatter. Again its invisible once installed
and that is how it looks from the bottom all stapled on.