Want to gain weight. Please suggest.

Gaining weight can be difficult but not impossible. The first step is to understand that you need to gain weight through lean cut muscle and not by eating fat, carbs which your body will metabolism anyway. Join a gym and opt for a moderate intensity resistance training. Add good amounts of protein and fibre in your diet which will help your muscles grow. Gym is important that your muscles grow aesthetically and in good shape. Sleep more than 7 hours a day. Workout tears your muscle and not sleeping 7 hours a day won’t repair your muscle and you won’t end up gaining weight. Keep yourself hydrated at all times. This can be judged trough the colour of your urine. If it is clear white you are properly hydrated. Avoid alcohol and smoking. It will considerably reduce your chances of growing muscles because they have a high amount of oxidants and break down anything that comes their way. Also since you are naturally lean it will be even further difficult. You need to correct your D3, B12, Iron, Calcium and phosphorus levels for a proper muscular growth. This is the brief idea. I hope this helps.