Hi KaitlynEich,
Welcome to the Support Communities!
The articles below may be able to help you with this issue.
Click on the links to see more details and screenshots.
iTunes: How to move your music to a new computer
http://support.apple.com/kb/HT4527
Using your Apple ID for Apple services
http://support.apple.com/kb/HT4895
I have purchased music, apps, or books with multiple Apple IDs. How can I get all of this content onto my iOS device?
First, you need to copy all of your purchased content so it is on the same Mac or PC with iTunes. This computer should be the one you sync your device with. For more information on how to move your content, see these articles:
Next, authorize your computer to play content with each Apple ID in iTunes. Once your computer is authorized for all your content, it can be synced to your iPhone, iPad, or iPod touch.
Downloading past purchases from the App Store, iBookstore, and iTunes Store
http://support.apple.com/kb/HT2519
Cheers,
- Judy