If you use Family Sharing, you can choose a family member's name next to Purchased to see their purchases.
Click the download button for the album or song.
How to redownload music on iTunes for Windows
Open iTunes.
From the menu bar at the top of the iTunes window, choose Account > Purchased. If you use Family Sharing, you'll see Family Purchases instead of Purchased.
Choose Music from the menu in the upper-left corner of the iTunes window.