Choose flat or fitted bed sheets in a large size and a dark color that will cover the stains. If you choose to use fabric, pick a thick fabric that will cover the couch's old color and any stains or tears in the sofa.
Cover the cushions with the pillowcase. Tuck extra fabric inside itself and fasten with a safety pin. Do this for each cushion.
Drape one sheet over the couch without the cushions. Tuck excess fabric into all the crevices. Push rolled-up magazines or PVC pipe pieces into the crevices. This will help keep the fabric tucked in smoothly.
Tuck remaining fabric under the couch. Pull it taut around the sofa. Fasten with safety pins and then replace cushions.