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 using a different Apple ID. Tap your account name, then tap Sign Out. 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 iPod touch 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.