My weight are less. ..any treatment that should be weight gain easely?

Depends on why. Gaining weight has a lot to do with number of calories that you take in(food you eat) compared with the number of calories you use during the day. If you have a medical condition that makes it hard to digest food, then you should talk to your doctor about your options.If you are a very active person,increasing the amount of calories you eat in a day will help. Are you sure you really need to gain?