You are supposed to eat 6 meals a day. A big breakfast, a snack, Lunch is supposed to be your biggest meal of the day, another snack, Dinner, and then another snack. Make sure your diet contains a lot of proteins since you want to gain weight. Hope this helps btw I got this info from a nutritionist.
i was anirexic and bulemea i know they are spelled wrong but yeah eat as much and as often as you can , but keep in mind make it healthy. or you can buy stuff from a pharmacy to make you hungray alot . hope i helped god bless