What is an effective way to gain muscle mass?

To build muscle do you need to stack up on protein/calories or both? Will you gain weight if you eat 2000 calories per day and eat like 75 grams of protein?(i weigh 145 lbs and am 15 yrs old). Currently i workout about 4-5 times a week with a break on the weekends. How many times a week should I work out my biceps, triceps, chest, and abs?

Tips/Advice?

What is more effective in weight loss free hand exercises or body building exercises in gym?

Hi friends I have joined gym before and had well toned body but due to carelessness and wrong eating habits I have put a lot of fat and my routine of regular gym has also been spoiled.So I wanna know that is it more effctive to go for free hand exercises or to go to the gym and have a heavy weight workout.The main quest is how can I burn my fat easily.I am on a dieting schedul too.