How to Redownload past iTunes purchases
View past purchases
In iTunes’ Account menu, look for a Sign In option; if it’s there, choose it, then enter your Apple ID and its password to continue. Otherwise, choose Purchased, or Family Purchases if you’ve set up iCloud’s Family Sharing feature.
Click on a media type, such as Music, near the top right to view past purchases of that kind. If you’re part of a Family Sharing group, you can click your name (top left) then a family member’s name to view their purchases.
Click the cloud icon next to the item you want to download. Once that’s done, double-click the item to play it right away, provided your Apple ID is authorized for playback on this Mac; if it isn’t, look in Account > Authorizations.