Old seat is faded and looking worse for wear so it needs a new cover.
Ok best way would be to what i have bought a never cover,
Do i rip the old original one off?
Do i glue the whole seat or just under neath and staple it in?
Remove the old one and staple the new one on. You'll have to stretch it tight as you go. You'll need a decent stapler and 1/4" staples. You will have to pull old staples out, so you can verify the length when you do that. I'm no expert, but I've replaced 3 of them now and they turned out pretty good.
its pretty hard to get it perfect. i would maybe use some spray adhesive to help keep it down, i ended up with a couple wrinkles after all my stretching. good luck!