How can I scream high and low vocal without being too loud?

Alright so I'm a metal head chick, I'm into deathcore, Metal ect.. You know the band Carnifex? Alright well listen to Dead against the gates, perfect example, well in the beginning I want to do that low of vocals and sound like that, and then in the song I wanna do the high one.. Can you teach me how to do it? I'm starting my own band "Decreased Souls" I wanna be the vocalist but also the drummer, so help me out! Thanks. :3