Updating billing info on itunes
Before you change your email address, it is important that you sign out of every other Apple device and service that uses your current Apple ID.
If your current Apple ID uses an email address that ends in @me.com, @or @mac.com, you might not be able to change your email address and the Change Email Address field will not be visible.
Under "Account settings" there is the choice to "Change your default shipping or billing info", click that link and then enter your Apple ID e-mail and password to login.
You'll see a box with the heading "Payment Information" under Account Information, click the Edit button there.
You'll almost always want to update to the latest and greatest as soon as you can. If it doesn't, though, begin by launching the built-in Software Update tool that comes with i Tunes. In fact, updates to all Apple software (and some third-party tools, too) are done using this program. When you install i Tunes on a PC, you also install the Apple Software Update program. When it comes to updating i Tunes, it can often be a good idea to first make sure you've got the latest version of Apple Software update. To update that: When the update has been downloaded and installed, Apple Software Update will run again and give you a new list of programs available to update.