All it takes is figuring out... Is it good or is it bad... If you can do this, you are ready for training!
Mostly, you know if something is wrong or right to do. So, in the YouTube video, he uses the terms "vice" and "virtue". It has been found that if you pair up a little something wrong with a right, your brain is of approval and yes, finds it healthy. The more you do this, the more healthy foods start to look attractive, and you begin to choose healthier foods... Thus, vice and virtue training works!