To download apps from the App Store on your iPhone and to sync it with an iTunes account, you need to have an Apple ID. Once you've associated an Apple ID with your iPhone, your phone references the iTunes account and App Store purchase history associated with that account each time you update or download new content onto your phone. However, if you've recently changed your Apple ID, or if you're the new owner of a previously owned iPhone, you can quickly change the Apple ID to the correct account on your phone through its settings.
1Tap the "Settings" icon on your phone and then tap the "iTunes & App Stores" tab.
2Tap the Apple ID displayed at the top of the screen. A pop-up dialog box launches with several options.
3Tap "Sign Out" in the dialog box to sign out of the current Apple ID on your phone.
4Tap the blank Apple ID field and enter the new Apple ID you want to use on your iPhone. Also enter the password in the appropriate field.
5Tap "Sign In" to complete the sign-in process.
- Information in this article applies to iPhones running iOS 6. It may vary slightly or significantly with other versions or products.