Cosco Alpha Omega Elite 5-Point 22-155 "removing watch back" Questions

REmoving carseat cover to wash it is an older Eddie Bauer 3 in 1 car seat that has recently been sick in. Without it I can go no where, not even into town as I have no one to watch the kids, so I have

...off please? as need to wash them but find the seat belt is stopping me? In most car seats, the belt can be removed from the back. This video might help: ...