In order to build muscle, you need to eat a calorie surplus; there are two ways to do this. I recommend eating an additional 300 calories per day above your maintenance level of healthy calories, but a surplus of calories from any foods will do. In doing it this way you will build muscle and see minimal fat gains. You can however eat a lot more than a 300 calorie surplus a day in order to build muscle faster but in doing so you will increase fat more rapidly. Muscle building if done right is a slow but rewarding process. Example below:
Maintain Weight = 2000 Calories a day
Muscle Building = 2300+ Calories a day
*Note: There will be unavoidable fat gains when trying to build muscle.
Ideally you want to lift heavy weight in order to build muscle quickly and most effectively. However you do not have to use weights to build muscle, you can simply do body weight workouts.
Not only is eating a calorie surplus a necessity, but you need to consume the required amount of macronutrients. Click here to learn more and calculate your macronutrients.