Mix floor cleaner with water in a bucket, following product directions.
Wash the stair treads thoroughly with a clean cloth and the prepared cleaning solution. A clean surface is important for carpet adhesion. Let the stairs dry before you proceed.
Remove the adhesive backing on one of the carpet treads. Center it over the bottom tread. Press it firmly into place on the stair tread.
Continue up the stairs, covering one tread at a time. Wait 24 hours before allowing heavy use of the stairs, as the adhesive needs time to set completely.