Hi..to gain it is very important to follow a proper well planned diet & exercise regime. Most people think that all this is for weight loss, but actually weight gain is much more tougher for the dietician as well as the client. A continuous monitoring of your daily diet & exercise routine is must, since the target is healthy weight gain (i.e muscle gain and not fat gain).
Next Steps
Meet a dietician for a detailed assessment to design you a proper diet plan with an exercise regimen.
Health Tips
Start with:
1. Eating balanced meals
2. Eat small energy dense meals every 2-2.5 hrs
3. Even if you are thin and job profile hazards , avoid excess intake of junk food (oily, fried, sweet stuff)