The Doritos: The Quest 3.4?

I'v been trying to complete the forth challange of chapter three of the Doritos quest thing, and every on talks about the sentince "three hidden points reveal the secret" and that you get the star map and that you flip it over to get a map of the U.S. and that you use the amulet to find three points and then go to the next challenge, but none of them tells how to get the sentence or what dose the amulet before geting it is for. So can any one explain me how to beat this challenge