Hi Julia D.
Welcome to the Support Communities!
The article below will explain how Apple ID's are used with various services like iCloud and the iTunes Store.
Do all of the members of your family share the same Apple ID for both?
Using your Apple ID for Apple services
http://support.apple.com/kb/HT4895
Here is some specific information for setting up the Messages app:
iOS: Troubleshooting Messages
http://support.apple.com/kb/ts2755
- Ensure that iMessage is turned on in Settings > Messages.
- To send and receive iMessages, your device must have a valid cellular or Wi-Fi data connection.
- iMessage registration validates your Apple ID for use with iMessage. If you are unable to activate iMessage, follow this article.
- If an iMessage cannot be sent, it will be resent using SMS or MMS, depending on the content. You can turn this behavior on or off in Settings > Messages > Send As SMS. Carrier messaging rates may apply.
- Verify that the Apple ID or phone number is listed in Settings > Messages > Send & Receive.
iOS and OS X: Link your phone number and Apple ID for use with FaceTime and iMessage
http://support.apple.com/kb/HT5538
I hope this information helps ....
Happy Holidays!
- Judy