Measure your settee--in terms of length, height and width--so you know what size sheet or bed spread to look for. A tape measure does the trick. Pull out that old sheet with the great paisley pattern or that bed spread stuffed away in the attic.
Drape the sheet or bed spread horizontally over the settee. This will cover most of the surface area.
Either stuff the ends of the sheet between the settee arms and the cushions, or, if the arms of your settee are stained, let the sheet drape over the arms as much as possible.
Tuck the sheet under the settee cushions for a more streamlined look.