Hi,
Your ideal body weight should be 50 kg, on the basis of your height. To gain weight you can follow a nutritious balanced diet, which contains a good quality protein like egg, chicken, milk, dahi/ yoghurt, soyabean, almond, cashew, sprouts etc and fresh fruits and vegetables. You can have calorie rich food like khichdi, rice kheer, soyabean biriyani etc. Drink 3 litre water per day and have a sound sleep about 6-7 hours.
Next Steps
You can chat directly with me on practo for further discussion.
Health Tips
You do some exercises which will help in metabolism, thus food intake will be more.