NATRC is the greatest thing since cheese in a can.
It is done off leg pressure indeed! Your horse may know how to do these things already. You have to figure out how to press the right buttons. Teaching them from scratch can be a little tricky. I would get someone to show you both how it's done. :)
You'll be stopped along the trail and asked by the judges for these movements. They may say, "Sidepass over that log," and you will, well, sidepass over that log. You'll know when you're required to do these things. The judges explain the obstacles well, and you can ask all the questions you want!