Measure the entire staircase with a measuring tape to determine how much carpet you will need. Measure the horizontal part of a step to find the width of the stairs, and measure the vertical part of each step to find the length. Add 3 inches to the length of each step.
Lay tack strips along the side of each step next to the wall. Staple the tack strips to the steps with a staple gun.
Place the carpet evenly along each step, and stretch it from the center of each step using a knee kicker. Use the knee kicker by positioning your knees on the padded cushion and applying pressure from your knees to the carpet. Hook the carpet onto the tack strips on each step.
Slide the knee kicker back and forth over each step to compress the pins. Trim any excess carpet from the staircase with a utility knife.
Ensure that the carpet is smooth and even on each riser, and then staple the carpet along the edge of each riser. Staple every 2 inches to make sure the carpet stays in place.