Eating alone will not help you gain weight. More calories must be consumed than used. Try to gain weight in a healthy way. Avoid junk food. Eat lots of fruits and vegetables. You should get evaluated for increased appetite and not gaining weight. Worm infestation, thyroid disorders, anemia, chronic illnesses all can cause this. Adequate exercise like muscle-building workout such as weightlifting and strength training may help. The medical advice given should not be considered a substitute for medical care provided by a doctor who can examine you.Seek medical help. Hope it helps.
Take care and good luck!