To set options for iTunes Store, go to Settings > iTunes & App Store. You can:
View or edit your account. Tap your Apple ID, then tap View Apple ID. To change your password, tap the Apple ID field.
Sign in with a different Apple ID. Tap your account name, then tap Sign Out. You can then enter a different Apple ID.
Turn on iTunes Match. If you’re a subscriber, tap iTunes Match so you can access your music on iPhone anywhere.
Turn off automatic downloads. Tap Music, Books, or Updates. Content updates automatically over Wi-Fi, unless you turn off the option in Automatic Downloads.
Download purchases over the cellular network. Turn on Use Cellular Data. Downloading purchases and using iTunes Match over the cellular network may incur carrier charges.