First off to gain muscle you need to up your caloric intake,depending on how much muscle you want to build, I suggest you get a caloric intake of 2,600-3,300 calories a day, but people who pack on extraordinary large amounts of muscle mass, including professional bodybuilders get at least 4,000-7,000 calories a day. However to insure you dont gain body fat, you cant just put any kind of food in you. You need to have a high protein, low fat diet, concentrate on getting1.5-2.0 grams of protein in you per pound of bodyweight on you everyday, get 2.0-2.5grams of complex carbs per pound of bodyweight on you, in you a day(good sources of complex carbs are oatmeal,noodles,rice,and whole wheat bread.) and start drinking at least a gallon of water a day. Another way to avoid gaining body fat is to space your meals out, if you try to get that kind of caloric intake in you using three meals, you will destroy your metabolism, and gain fat, so instead space them out into 6-8 meals a day. Also you will not be able to get your required protein intake in you just through you meals, so do this, eat a meal, then an hour, and a half later drink a protein shake, then an hour,and a half later eat another meal. Do this all day until you have 6-8 meals in you, and 6-8 protein shakes in you everyday. It requires alot of discipline to do this but if you want to gain muscle you'll have to do it, unless you want to take steroids. If you cant get a meal in you drink a meal replacement drink, it has the necessary amount of calories, carbs, and protein, to replace your meal. Some good supplements are protein shakes,meal replacement drinks,L-glutamine,creatine, and vitamins. Follow this diet, and supplementation program and in six months to a year you wont know yourself. Unless you want to use steroid, be patient, and understand something you need to have, to build the body you want, but cant buy on a shelf is time. By the way if you are eating in the manner I described to you, you better have one hell of a training program. And also be sure to do at least 30 minutes of cardio, a day, your new diet will help you burn your bodyfat, but you do still have a significant amount of bodyfat to loose, just judging from you picture. I use to be 255lbs, at a 46" waist, I got down to 153lbs at a 32" waist, and then up to 175lbs at a 32" waist, without putting on any body fat, and I did in a little under a year without steriods. Diet,weight training, and cardio are the three keys to loosing bodyfat, and putting on muscle. I was only 18 at the time so my testosterone level were high, but if your in college, and are weight training, the subject of steriods will probably come up. Your young enough not to have to use them, but by using them you would be able to do in four to six months, what it would take you up wards of around a year to accomplish. If you do decide to use them look for legal alternative, like clinical prescriptions, or steroid precursors. Small amounts of steroids, when used wisely can be a safe, and healthy way to gain muscle, and loose body fat quickly. But everyones body is different. I believe it is a personal decision, but should be an educated one.