You can look into using creatine before your workouts, it helps build muscle mass. I have used it and so has my partner, who is 100lbs soaking wet and very thinly framed, we both felt it worked as intended.

I think it'll be less cardio that you need, and more so strength training. The video that @(you need an account to see links) posted is awesome and a great start!

You're going to have to get that heart pumping and that body moving to gain any muscle, so find something you love that also happens to give you a workout. Horseback riding, rock/wall climbing, bicycling, hiking, tennis/hardball, etc. Find out what excites and motivates you (and gets you moving!), the muscle gain will come along with it!