Most colleges/universities have cheap personal trainers available for booking. These are usually students in a kinesiology program, and they usually know their stuff.
GET A PERSONAL TRAINER, if only for a little while to get yourself acquainted. They will help you create a workout suited for your body and needs, and ensure that you are doing things with the proper form.
Too many people hurt themselves when trying to plunge into a workout routine alone.
Once you've gotten the hang of it, get rid of the trainer. Research more exercises....
http://www.exrx.net is an amazing resource. Keep your diet balanced - protein and carbs should be about the same amount, with fat about half of those... like 40% 40% 20%.
To build mass, ensure that you are taking in more energy in food than you are putting out in exercise.
You can consult a food guide to see how many calories you consume, and add up how many calories you burn throughout the day.