Hello Diddywong,
Thanks for using Apple Support Communities.
From your post I see that you need to download a purchased song from the iTunes Store. To download your previous purchases, please follow the steps outlined below.
Make sure your Mac or PC meets these system requirements:
- iTunes 10.3 or later
You need iTunes 10.6 or later to download previously purchased movies and TV shows.
- iTunes account in a country where iTunes in the Cloud is available
- Open iTunes and go to the iTunes Store.
- Click Purchased in the Quick Links section.
- Select the content type that you want to download (Music, Movies, TV Shows, Apps, or Books).
- Select Not in My Library to view purchased content that isn't on your computer.
- Find the item that you want to download. You can browse using the menu to the left. If you have more than 2,000 songs, you'll see Recent Purchases instead of All Songs or Albums.
- Click the Download icon next to the item you want to download.
If an item is already in your library, the Download icon won't appear.
Download past purchases - Apple Support
Take care,
Alex H.