Summarize the following:
When it finally comes time to lay your carpet runner, it's best to start at the very top and work your way down. That way, you'll have gravity on your side, and it'll be much easier to cut any runoff carpet at the end. If you traced the carpet outline at the beginning of the project, it should be an easy matter of getting the carpet situation between the two as close as you can. Take care to press the carpet under the nose and tug the rest out to make sure you're getting just as much carpet as you need. Work down to the last step; when you're done, the carpet should be covering the expected ground, but the outline of the steps may not be fully visible. Make sure each step is as good as it can get before you move down to the next-- any mistake will cause a load of undue strain later on once the project is supposedly complete. A carpet knee-kicker will get the carpet planted firmly in areas that may be otherwise difficult to reach.  Place the front edge of your carpet knee-kicker on center of the runner about two inches from the riser and apply pressure until the carpet is locked in. They can be remarkably satisfying to use, and will give your stairs a much tighter look than if done without.   Lean on the front knob of the kicker with one hand, and use the other hand to keep the kicker's shaft level.  You can also use a carpet chisel. The dull edge helps tighten up corners and is easier to use on stairs or in tight quarters. As with previous steps, the last part of using the knee-kicker should be making sure you got the job done to your satisfaction. Without kicking in properly, you may have too much carpet or too little, and it'll require uprooting or even destroying the progress you've made. Before you move on, you should ensure that the carpet is being snagged by the tackless strip at the far end of the tread. If the tackless strips aren't properly clinging to the carpet, it could result in the carpet getting bumpy a few years down the road. Using a chisel or other thin tool, press the angle between the step's height and tread to make sure it's getting hooked in. At the bottom, there should be a little bit of runoff. From here, it's just a simple matter of cutting the excess carpet away with a carpet knife. Feel free to do what you will with the remainder of the carpet. Some people are quick to throw them out, while others like to find practical uses for them. Having a powerful stapler designed for home improvement is necessary to finish things off and get your carpet snug and perfect. When stapling, push stapler through the carpet pile and against the backing before pulling the trigger.  Staple on the underside of the step noses, and nearest the angle between the tread and height. Staple at three inch intervals for optimal stability. Alternatively, you can use carpet glue instead of staples. Make absolutely certain that the carpet is exactly where you want it to be before you staple. After you staple, it will be next to impossible to correct any mistakes.

Summary:
Start at the top of the staircase. Place runner between layout pencil marks. Press your carpet into the outline of the steps with a carpet knee-kicker. Verify the kicking is complete once you're done. Verify your work is correct. Carefully cut any excess carpet at the bottom of the steps. Staple each step through to the wood.