How do i setup a new itunes/app store account on my iPhone?

I bought the I-phone 3g yesterday.


I set it all up and everything has gone fine.


Although when i enter the App store or Itunes and try to purchase it will only let me sign into my brothers itunes account, not mine. I cannot find anywhere to change the e-mail so i can log into my account.


Can anyone help my please??
How do i setup a new itunes/app store account on my iPhone?
new app acct: http://support.apple.com/kb/HT2534


faq: http://support.apple.com/kb/HT2001