Write an article based on this "Click the small profile icon next to the "Search Store" bar. Enter your Apple ID information, or click . Deauthorize an old computer (if necessary)."
This will open the Apple ID login window. Create Apple ID. You will need to be logged in with an Apple ID in order to download items from the store. Creating an Apple ID is free, but requires entering credit card information. Click here for instructions on creating an Apple ID without a credit card. You can have five computers associated with your Apple ID at once. If you are setting up iTunes on your sixth computer, you won't be able to authorize it to download your purchased content. You will need to deauthorize one of your older computers, or deauthorize all of your connected computers at once if you don't have access to them anymore.  Click here for detailed instructions on authorizing and deauthorizing.