How you use it is entirely up to you.
Three scoops is about 110 grams or about 450 calories. A “meal” is actually about 127 grams, and 500 kcal.
All Huel really promises to be is as nutritionally complete as they can make it. That means if you figure out how many calories you need in order to survive and measure that much out and eat that (and nothing but that), you should be doing quite well.
If you want to have one meal per day, that’s fine. I like Huel because it’s better nutrition than I normally eat (bad Will, no biscuit!), and because I can count calories REALLY easily to know when I’m eating enough, or too much.
There’s no right and wrong way to consume Huel. It’s kind of like saying “I bought a bunch of bananas. How should I eat them?”
You can eat one a day, raw, peeled and eaten. You can make Bananas Foster. You can make a banana split or a banana milkshake.
It’s a food. It’s a food with some nice qualities, but it’s still just a food, how you eat it is really up to you!