How to develop chest voice?

I'd say I have a pretty good head voice: it sounds good, I'm gradually getting louder, and I am developing vibrato. (By the way, I'm a thirteen year old female. I'm not sure if I'm a soprano or mezzo. I don't know all the notes I can hit.) I have recently been listening to Broadway singers and I want to learn how to use chest voice. Whenever I use it, it sounds forced, I can't high notes and it just altogether doesn't sound good. I know how to sing with my diaphragm and I know what mixed voice is, but I don't know how to use it. Please Help!