Remove the seat cushions from the couch. If the couch has removable back cushions, adhere the cushions to the couch with a few fabric tacks or stitches.
Drape the sheet over the couch and tuck it snugly into the couch. Leave plenty of fabric covering the back, arms and front of the couch. Starting at the top and back corner of the couch, pull the sheet tight and pin with a fabric tack. Work your way to the base of the couch and then repeat starting at the opposite corner. You will use approximately 30 to 40 tacks.
Cut the second sheet into three equal parts. Cover each cushion with a third of the fabric, pull tight and pin. You can also hand stitch the underside of the cushion to secure the fabric. Repeat with all three seat cushions.