iTunes Family Share not working

I recently had my dad start a Family Plan on iTunes which enables him to share music, apps, etc. with my iCloud account. However, when I go to where the shared music would be (under the Purchased section on iTunes), it comes up with a message that says "this iTunes account is not set up to use Family Sharing." The weird part is, my dad can see my purchases but it's just I can't see his. All of my music has been purchased under his account over the years, and since I'm going off to college soon, I'd like to have my music. How can I fix this?