Use a measuring tape to find out the length of your sofa. Finding the length of the couch will help you determine the amount of sheets needed to cover your sofa. You will also need to take a measurement of the couch's height and the width of the seating area and cushions. Make sure the sheets you use are close in color to the sofa so your cushions will blend in with the new sheet without needing to be covered.
Take all the cushions off the sofa. Place the bed sheet over the sofa. Remove all of the wrinkles by running your hand over the sheet to smooth them out. Tuck the sheet in the corners of the sofa to secure it in place.
Stick fabric tacks through the sheet to the sofa. Make sure the tacks are in locations where they will not be noticed.
Take the end of the bed sheet that touches the floor and tack it to the underside of the sofa. In order to tack the bed sheet to the arm rests you have to carefully tack the sheet to the underside of the armrests on both sides of the sofa. Only use tacks that are a similar color to the sheets you are using on your sofa.