Measure the sofa and love seat separately. Measure the height of the back, sides, front, the length, width and depth of the cushions and armrests. Compare them to the size charts where you are ordering your slipcover from. You can also order a custom-made slipcover. Sofas with wooden arms, single seat cushions or camel backs will need special slipcovers.
Slide the slipcover in place and tuck it in around the edges so it is tight and smooth. Your slipcover will need readjusting as the sofa is used, since they shift out of place. Periodically, pull it back and tuck it in.
Add new accent pillows to the sofa. Use bright or patterned cushions if you chose a solid, simple slipcover. If your slipcover is more elaborate, choose simple accent pillows.