If your goal is to build muscle mass fast, then you are facing a real challenge. Get ready for hard work and strong commitment to your goal. But don't get scared, this goal is not as unreachable as it might seem. I just want to warn you that you are about to enter a new life style that demands lots of changes.
No muscle mass can be built without a special diet. To become bigger you have to eat way much more than you are eating now. Muscle building materials are mostly proteins. The perfect amount of proteins per day is 1 gram to maximum 2 grams per pound of body weight. But don't get too exited about eating proteins, as there is a limit your body can metabolize. Eating more than 2 grams per pound per one day won't bring you any benefits.
The second thing to do is to find a professional trainer, who will help you to create a personal training program to build muscle mass fast. There are also many internet training programs and books that can really give you lots of advice on how to reach your goal.
To build your muscles fast you have to know that low weights are more suitable to keep your body in shape. To get big muscles you will have to work with really high weights. To understand why, I will give you the explanation. During the work out, the muscle gets micro traumas. The muscle responds to that trauma during the rest period. It's when the muscle grows. When you are working with heavy weights you are creating the bigger trauma. This way the muscle grows faster.
Please use your knowledge wisely not to harm your health, and consult with your doctor before doing any exercises. Good luck with your goal!
Source