Sweep all dirt, dust and debris off the stairs. The treads need to adhere to a smooth surface to prolong their lifespan.
Clean the stairs with warm, soapy water and a cloth or sponge if desired. Wait for them to dry completely before continuing.
Measure the width of your stairs and the width of the carpet tread pieces. For an example, assume the stairs are 26 inches and the treads are 20 inches, leaving 6 inches of space. Divide the remaining space by 2 to determine how much space to leave on each side of the tread for an even application. In the example, place the tread 3 inches from each edge of the stair. Mark the 3-inch mark with a pencil for reference.
Peel the backing off the tread, if they're self sticking, line them up properly on the step in between the pencil marks and then press down. If they're not self-adhesive, stick a piece of adhesive carpet tape to each step in between the pencil marks. Cut the carpet tape about 2 inches shorter than the measurement for the tread, leaving an inch from the edge of the adhesive to the pencil mark on each side.