All boys wanna access Media Library (sung to All Gurls Wanna Have Fun)

Howdy. I'm trying to access media from a users song library and receive:

<ICUserIdentityStoreACAccountBackend: 0x148f8af30> Failed to initialize active account, error=Error Domain=ICError Code=-7013 "Client is not entitled to access account store" UserInfo={NSDebugDescription=Client is not entitled to access account store}

I'm told I need to add a Media Library Access Capability. Nothing like this shows up in Xcode under Signing & Capabilities > +Capabilities. Also I can't find anything like this in my account in dev.apple.com.

How do I enable myself and a test user using another iPhone device to access my music and their music respectively?

Thanks!