Where do I manage my Apple ID email / password?
Apple uses your individual Apple ID to authenticate purchases, authorize computers to play content and determine where to send important information such as invoices. Your Apple ID can be used for services in iCloud, the iTunes Store, App Store, iBookstore and iChat.
Full control over managing the Apple ID takes place on a computer. To access your Apple ID account information and profile navigate to the following web address:
Name, ID, and Email Addresses
Password and Security
Language and Contact Preferences
Newest iPhone FAQs
Don't forget that if you change your Apple ID or password you'll have to update any iOS devices or iTunes accounts on your computer to reflect the new information.
Enter new Apple ID information on your iOS device by navigating to Settings -> Store -> Apple ID.
Enter new Apple ID information into iTunes on your computer using Store -> Sign In.