Remove the seat cushion from the chair by flipping the chair upside down and unscrewing the seat.
Pull off the old seat fabric, using pliers to remove any staples or nails holding it in place.
Place the old fabric on top of the new fabric and trace the old sizes onto the new. Do the same to the old and new pieces of padding.
Cut out the new pieces of fabric and padding and position them on the seat.
Fold the fabric tightly in place and staple it onto the seat.
Put the seat back onto the chair and screw it into place.