Prepare and Cover Seats
Turn the chair upside down and remove the screws holding the cushion to the seat.
Remove the staples from the underside of the cushion with the flathead screw driver. Use the fabric as a pattern to cut the plastic for the cushion.
Place the plastic, fabric and cushion (in this order) on your work surface. Start on any side. Fold the fabric and plastic around the cushion, making sure to leave slack for the other sides. Staple into place. On the opposite edge, do the same. Make sure the fabric and plastic are taut. Continue with the other two sides.
Once the sides are complete, start on the corners. Experiment with folding the corners until you find a fold that looks neat. Staple into place and fold the other corners accordingly.
Reassemble the seat cushion to the chair, aligning the screw holes. You may have to poke holes in the plastic and fabric to allow for the screws. If so, you can use an ice pick or the screws themselves.