As long as you're comfortable with Lesson #8, Seeing Right and Left, you should be able to start tracking along a wall or flat surface. Try to find a wall that you are familiar with, it can be indoors like a long hallway or outdoors against the side of a building or solid fence. It should be something that doesn't have a lot of other obstacles around, like trees or furniture or other objects and should be free of danger. A straight stretch of wall with no windows or doors would be best.
I like to calibrate to my surroundings first by clicking around and getting accustomed to the environment. Approach the wall first and click to echolocate the wall. Turn one direction and then the other, still clicking to get a feel for what the wall looks and "feels" like. Move toward and away from the wall and verify that you know how far from the wall you are by reaching out to touch it with your hand or cane.
Turn in the direction you are going to walk and get comfortable with the sound of the wall on that side of your body. Once you are comfortable with the sensation of the wall, start walking alongside the wall and try to maintain the same sensation on that side of your body. Move slowly if you need to at first, and remember, since you have already determined that the route is free of dangers, you should refrain from reaching out to touch the wall even if you think you are going to hit it. If you get a strong "close" sensation on the wall side, just pause a moment and take a step away. Gradually increase your speed as you become more comfortable doing this.
If you are in a hallway, you will have walls on either side of you which may be a bit easier because I think getting dangerously closer to an object is easier than detecting getting farther away from an object. But the principle is the same either way. Just try to maintain your proximity to the wall or walls.