Ok you don't have to take my advice if you want, but here's what I have to say.
I'm 5'10, 170lbs and around 10% bodyfat, so a pretty good build atm.
1) Avoid cardio if you want muscle, it's virtually impossible to gain muscle and lose fat at the same time.
2) Eat at a caloric surplus, probably around 2300 calories a day for you, and if you can then try and get 1g of protein for every lb you weigh (I believe you said 140lbs, so 140g of protein a day)
3) Lift heavy, probably a 5x5 routine, so 5 reps of the heaviest weight you can do, then do this 5 times (5 sets).
4) Get a proper routine, I hope you aren't just doing pushups and stuff in your bedroom, look up Rippetoe's starting strength, or just browse bodybuilding forums.
5) Ignore people saying avoid supplements, whey protein will make this process a whole lot quicker (creatine too if you want). Whey protein provides a different job to natural sources of protein like chicken etc. as whey protein is digested in your body much quicker, so feeds the muscles when they need it the most (right after your workout), whereas if you were to eat a chicken breast post-workout it would take too long to be broken down and feed the muscles.
6) Forget the people saying you're too young, which I started earlier :p