You hold the comb at an angle almost level with the skull so that the point and part of the flat surface of the comb come in contact with your scalp. Think of this as using a comb to exfoliate and massage your scalp. With this in mind you're going to lightly scratch the surface of your scalp in a tiny back and forth motion without lifting the comb (like you're scratching an itch).
Begin at the hairline in the front and work backwards towards the crown. Once you get to the crown begin again at the hairline but move a little to once side to begin a new path to the crown. Continue moving about the head in this manner, finishing one side all the way to the back and then come back to the front and begin the second side.
You should lean your head slightly towards the direction you are scritching. So if you are scritching the right side, lean your head to the right. The only exception is when you get to the back, at that point it is easier to tip your head forward and let the hair fall over your face. It should feel really good. Some places on your scalp may beg for a bit more attention (like when you are getting a good massage and someone finds a spot that really needs work) and as long as you aren't using too much pressure (you don't want to damage your scalp) go ahead and rub that spot.
You can also follow with a massage of the scalp using just your fingertips.
I hope I've explained it in a way that is easy to understand. It's easier to show than to explain.