Some family members may want to share an Apple ID for purchases made in the App Store, Music Store, or iBooks. This allows the purchased items to be used on their separate devices without the need to purchase them twice. However, users will often want to maintain separate iCloud accounts, so their personal calendars, contacts, etc., don’t get mixed together.
Fortunately, it is easy to use one Apple ID for iCloud and another for purchases on an iPhone, iPad, or iPod touch. Go to the device settings by tapping SETTINGS on the device’s home screen.
Once in Settings, scroll down and tap ICLOUD.
If you are already logged into the iCloud account that you wish to use (the current ACCOUNT, if there is one, will show at the top of the iCloud settings), then you can skip these iCloud steps and move onto the App Store steps below. If not, either enter your Apple ID and password to log in, or tap GET A FREE APPLE ID to create a new one. If there is an Apple ID already logged in, but it is not the one you want to use for iCloud, scroll to the bottom of the iCloud settings, and tap DELETE ACCOUNT. Then log in again or create a new Apple ID.
Once iCloud is logged in correctly, tap SETTINGS in the upper left to return to the main Settings list. Scroll down and tap ITUNES & APP STORE.
If the current APPLE ID is not the one you wish to use for purchases, tap it, then tap SIGN OUT. Sign in with the correct Apple ID. This will be the Apple ID logged in for purchases and downloads in the App Store, Music Store, and iBooks. Now, whenever an app, song, video, or book is purchased using this Apple ID, it will show up as available to download for free on any other device also logged in with this Apple ID.
If sharing an Apple ID for purchases, you will likely now want to scroll down and turn off AUTOMATIC DOWNLOADS. This will prevent items purchased on other devices from automatically downloading to this device.
Jason Merrill, Mac & iOS Consultant