I'm not sure there is a "correct" way to do it. There's lots of variations that work differently for different people. But even at its simplest (fasting 16 hours, eating for 8) doesn't really require a ton of extra planning. The point is that during the 8 hours, you fill up about as quickly as you do when you don't fast, so you don't really end up consuming more. What does change is you remove the snacking/overeating that occurs throughout the rest of the day. So even if someone eats the way they normally would during their 8 hour period of non-fasting, many people will see benefits.

Obviously there's lots of other additional dietary steps one can take, but most of them don't actually differ much from traditional healthy eating advice: limit carbs and sugar, balanced meals, don't drink your calories, etc.