How Do You Cook Ration Packs?

I left cadets really young and can't remember anything, do you boil the bags or put boiling water in the bags OR is it different for different meals? My fav meals are Beans & Bacon, Sausage and Beans, Hot Pot, and Meatball Pasta. I've been looking all over to find how to cook them but it seems like you're just expected to know! lol help I'm a dunce! (I'll be cooking them on a hex burner if that helps)