Identify the retaining clip that holds the rear view mirror in place. It is located at the base of the mirror mount and will likely require a flathead screwdriver to pry it off.
Use a flathead screwdriver to pry the retaining clip off of the rear view mirror mount.
Once the retaining clip has been removed, the rear view mirror will be free to be lifted off of the mount.
Be careful not to let the rear view mirror drop as it may break.