Usually when guys (or girls) are wanting to pack on some muscle and get 'tanked', they mostly think about 2 things - gym and protein. While those two things are vital for packing on muscle, there is something that so many people overlook.
Everyone knows that protein is vital for muscle building, but there is something else, something that seems to be forgotten. To get 'hench', you need to up your overall CALORIE intake. Most people tend to eat a fair amount of protein, coming from food and shakes, but don't think about the overall amount of food. If you google bodybuilding diets, you will see that a very common meal is brown rice and chicken. Bodybuilders eat a lot of carbs, but brown rice is a favorite. They do however change this if they are leading up to a competition, but that's another story. Bodybuilders will eat a lot of protein, but also vegetables and carbohydrates. If you don't eat enough calories, you won't get big. A typical bodybuilding diet will contain between 3000-7000 calories per day depending on age and size. They don't do this purely because they love food, they do this because its a 'must-do' thing to be 'big'.
When it comes to adding size, you don't really need to calorie count as such, you just need to eat a lot of healthy, lean foods. I'm not saying you should eat all day every day, but you want to try and eat every 2-3 hours. If you are training in the gym regularly, lifting heavy weights, eating protein, but aren't noticing the gains you want to be seeing, then try upping your overall calorie intake, you should notice a difference!