First, contact your local dealership and provide them with your VIN number to confirm that you do in fact have removable headrests.
Second, find the button on the headrest post. On the opposite post, you should see a tiny slot that you can stick a clothing pin or needle into. (See photo attached).
While pushing the button with your thumb and pushing the needle into the slot with your other thumb; have someone pull the headrest up and it should come right off.
Simply slide the headrest prongs back into their slots once the seat cover is installed.