take the advice of these guys, start light, nail out proper form. you're in a great position now, because you've got no bad habits to break as far as performing different exercises. performing exercises properly is either going to make you or break you, literally, as improper form can lead to injury. good luck and start off slow and easy, you've got many years ahead of you to build and grow.
i think my light weightlifting as a young teen helped to build my frame into what it is now, and i only got into it on and off over the years until just a few months ago when i started getting serious. best of luck to you, and from the few short weeks i've been surfing and posting on this site, i've found everyone to be excellent in terms of advice and knowledge. stick around here, these guys and gals will help you out tremendously.