My experience with seat covers is limited to Gen. 1 Foci. In order to remove the seat cover, the seat must first be removed from the car. If it is a front seat, remove the four T-45? bolts from the seat frame rails. Then the wire harness underneath the seat must be unplugged, and, since that harness has SRS (air bag) wiring, the battery should be disconnected to prevent accidental deployment, and/or turning the air bag light on.
The cover fabric is held to the seat pan with " hog rings" which are circular wire rings that need to be bent open with pliers (needle nose worked best for me) and rotated out of the attachment points on the seat pan. The front passenger seat cushion also has a pressure sensing pad beneath the cushion, which turns the passenger side air bag on, so be careful with that. Again, this is from my experience with Gen. 1 Foci, only. Perhaps some Gen. 2 members will chime in on their experience. Good luck.