What do i need todo?

Okay im 15 years old, and im an okay/decent singer. Im more of a screamer, i scream the correct ways. To make sure no vocal damage, but I need to learn how to sing better. I can sing grunge, to saosin or dance gavin dance. I dont know scales or ways to sing, but i do sing correctly (so im told) with my stomach, since it tences up or flexes when i sing. I need to know how to learn this. i dont know where to take lessons or where to find a vocal coach, I dont have alot of money. Just alot of will power. thanks