Controlling my singing voice?

Hey there, I'm 13 and my mom wants me to sing a spanish christian song called "Eres mi respirar" "You are the air I breathe" in English by Hillsong. Anyways she wants me to sing in at church on Sunday by myself on April 1. I have a very powerful strong voice, I just cannot control. Any practices that would help, I'd be glad to take! Please and thank you!