Your weight will always depend on your height. Have nutritious food comprising of vegetables, fruits, dairy products, pulses, cereals, nuts, dry fruits, and if non-vegetarian then poultry, fish…all will help you increase your weight. Have sufficient quantity of water everyday (around 7 to 8 glasses of water). Do not skip you meals. Avoid canned, processed and junk food. Sleep 8 hours daily. Integrate some simple exercises in you routine as it will keep you fresh and active. If you addicted to tobacco or alcohol then quit.