As the saying goes "keep singing and reaching for the stars".... (thanks Casey Kasam.)
Practice, practice and more practice.
You also have to be comfortable up on stage and you can if you find "the zone" of your song. Sing something you believe in and tell the story that the song is about. For example, I sing alot of Evanescence because I'm able to pull from my soul what the lyrics are saying and I have lots of life experience to find the thing I need to perform their music. I find a dark place in my life and suck myself into it to sing their music. Once you find the zone you can block out anything but the music and it comes naturally from there.
If you have the talent and the ability to grip the audience, then all that's left is confidence. You have to be a bit braggish and be able to back it up.
The youth are making lots of waves now a days in music so don't let your age keep you from your dreams. Look at Charlotte Church, Josh Groban and the likes who all got their starts at very young ages. Heck look at Michael Jackson. He fronted a group before he was a teen.
... then keep reaching for the stars....cause you never know you just might get there someday!
an Alaskan DJ/KJ