How can i gain weight and add muscle mass?

Gain Muscle Mass: You are what you eat. Consume more protein and add exercise and you gain muscle. Overeat carbs and fat and don't exercise and you gain fat. You should eat 1 gram of protein for every pound of ideal body weight. For instance, if your ideal body weight should be 180 pounds, then you should eat 180 grams of protein a day...As long as you don't have any kidney disease.