HOW TO AUTHORIZE YOUR COMPUTER TO USE iTUNES

You must Authorize your computer before you use it to sync or play content that you download from the iTunes Store.

When you authorize your Mac or PC, you’re giving it permission to access your apps, audio books, books, music, movies, and other content. You can authorize up to 5 computers, which means that you can play your content on 5 different computers. You can authorize a computer only through iTunes on that particular computer. You can't authorize a computer from another computer or from your iPhone, iPad, or iPod touch.

How do I authorize a computer?

1. Open iTunes on the computer you want to authorize.
2. Choose Store > Authorize This Computer from the menu bar.
   You might need to show the menu bar to see this option in Windows. In earlier versions of iTunes, you can access this option from the Advanced menu.
   
3. Enter your Apple ID and click Authorize.

If iTunes asks you to authorize your computer again, it won't use a new authorization. iTunes uses the same authorization for the same computer. 

What happens if I run out of authorizations?

If one of your 5 authorizations is on a computer you don't use much anymore, deauthorize it. If you've sold or given away a computer that used one of your 5 authorizations, you'll need to deauthorize all of your computers and then re-authorize each one you still use.

Windows users:

If you didn’t deauthorize your computer before reinstalling Windows or upgrading your RAM, hard disk, or other system components, your computer might be using multiple authorizations. Try deauthorizing your computer a few times until it’s no longer authorized, then authorize your computer again, and it will use only one authorization.

How do I know how many computers I've authorized?

If you've authorized more than 2 computers, you can see how many are authorized.

Open your account in iTunes and sign in with your Apple ID. (Or, open iTunes, click Store > Sign In, and enter your Apple ID and password.) In the Apple ID Summary section, you’ll see the number of computers that you’ve authorized with your Apple ID. You can’t see the names of those computers. 

Do I need to authorize my iPhone, iPad, or iPod touch?

No. You don’t need to authorize your iPhone, iPad, or iPod touch, but you do need to associate your iOS devices with your Apple ID. Your iOS devices don’t use your available authorizations.