So this is how to cut hair with notching scissors, or I refer to them, actually, as thinning scissors. The difference between these scissors, as you can see, there's one blade that's straight and one blade that's perforated. What this does is, instead of creating a straight, blunt line, it gives you a more diffused feeling to the hair. It only takes off half the hair, as opposed to using a scissor.
So how would we use this? Take a section. You see I take a horseshoe section around. Pull straight out, nice tension, and put the scissors in. Now bearing in mind where you want the weight to come from, the closer you go to the head, the more volume you'll create. So if you want to create volume at the root, you would start in towards the scalp. If you want to take weight out from the ends, you would literally just do the same thing, but starting towards the end.
So you see, you keep the same length in the hair, but you've removed this much weight. That's how you cut hair with notching scissors.