I haven't made it in years, but the powder (vital wheat gluten) is basically flour with the starch removed. There's a lot of recipes out there, but the idea is to make a flavored dough out of it, then simmer it in a broth for at least half an hour. The tricky part is you don't want it to fully boil, or the texture will be off. You need keep checking on it to keep it at a low simmer.
I should mention that while it does have a lot of protein, it's the same type of protein as the pasta. It doesn't really matter for a single meal, but it's not a complete protein. Long term you need other sources to get all your amino acids. There's a reason a lot of staple meals have a combination of grains and legumes.