You need to remove the O-rings and bottom and middle hooks, then the whole spring kinda swings around on the top hooks.
From then on out the easiest way to do it is to open both rear doors, lay on your back on the back seat with your head pretty much inside the seat cover that's unzipped and look straight up. You will see the hooks and the loops they are in, and all you need to do is push up and they will pop out. Might take some effort as they are wrapped in paper and it has a tendency to rip and get stuck in the loops. Just wiggle it around and push upwards.
Also, remove the headrest before you do anything as it might affect visibility inside.
If you are doing this without alot of lighting i recommend a flash light in your mouth