Q: Authentication Required

Hey Mikaela Arsenault!

Here is an article that seems to describe your issue and will help you troubleshoot it:

iCloud: Account troubleshooting

http://support.apple.com/kb/TS3988

I receive a “failed user name or password” alert when attempting to sign in at iCloud.com, in iCloud preferences (Mac), or in the iCloud Control Panel (PC).

• Make sure that you're entering your entire Apple ID when you sign in (for example, if your Apple ID is username@me.com, make sure that you aren't trying to sign in with just “username”).
• Verify that the Caps Lock key is not enabled. All passwords are case sensitive.
• Make sure that you're using the correct iCloud-associated Apple ID and not a different Apple ID used for other services. For more information about having more than one Apple ID, refer to Using your Apple ID for Apple services.
• If needed, reset your Apple ID password at iforgot.apple.com.

If you use the same Apple ID for iCloud as you do for other Apple Services, (for example, Apple Online Store, iTunes Store, or Mac App Store), changing your iCloud account password also changes your password for the other Apple services. Make sure that you sign in to those services using your new password. Also, be sure to update your Apple ID password on all of your devices and computers that may use your Apple ID (such as any email applications that you use to receive iCloud email).

Thanks for using the Apple Support Communities. Have a good one!

-Braden