Hi jmb8989,
Welcome to the Support Communities!
Does your wife have an AppleID for her iCloud already? If so, she would use the same AppleID to sign in to the iTunes store. If not, here is the information to add or change and Apple ID:
http://support.apple.com/kb/HT4895
Frequently asked questions about Apple ID
http://support.apple.com/kb/HT5622?viewlocale=en_US
How do I get an Apple ID?
You may already have an Apple ID, and you only need one for everything you do with Apple. If you aren't sure, visit My Apple ID and click Find your Apple ID.
If you don't have an Apple ID, you can create one at My Apple ID. You can also create one by signing up for an Apple service (such as an iTunes Store or iCloud). You should use your primary email address as your Apple ID.
You do not need to create a separate Apple ID for each Apple service. A single Apple ID can be used to access all other Apple services.
I hope this information helps ....
Happy Holidays!
- Judy