How do you change your name legally?

Im 15 years olf and i hate the spelling of my first name, so when i get older i want to change it.



How old do i have to be to change my name without my parent permission and where do i go to do it? Will it cost?

If it help i like in Sydney.

ThankyouHow do you change your name legally?
more then likley you have to go to the courthouse to change it and yes i think it will cost you something