Measure your stairs. If you are merely going to install the runner yourself, you will need to know how wide and long it should be (the average width is about 2 feet 6 inches), but if you will be sewing it yourself, it is even more important to get accurate measurements. Your runner should fit in the center of your staircase with an equal amount of space on either side.
Cut or sew your runner down to size. If you are sewing your own runner, choose a thick material with a friction-inducing texture. Apply a carpet backing or a padding to the back of the runner you are making then sew it into place. If you are simply installing a runner, cut one end in a strait horizontal line.
Carefully align the edge of the runner to the bottom lip of the top step.
Use a nail or staple gun to hold the runner in place.
Move backward down the stairs, stapling the runner along the corners until you reach the bottom. At this point your runner should be pretty firmly attached.
Cut any leftover bits of carpet off of the runner after stapling down the end.
Go back to the top step and apply an adhesive along the edges of your runner as necessary. You should also staple down the sides. Using both a waterproof adhesive and staples will ensure that your runner does not move.