Apple Music

The Family Organizer may have also given you the option to share his iCloud Storage. What happens if you try the steps in the iPhone section of 'How to listen to Apple Music on all of your devices' in:

Join Apple Music on your iPhone, iPad, iPod touch, Mac, or PC - Apple Support

If you accepted the invitation, then see the 'Explore the Apple Music app' section in:

Listen to music and more in the Apple Music app - Apple Support

If you can't accept the invitation, then you should be able to accept it kin your Family Organizer's device. See 'If you can't accept the invitation' section in:

Set up Family Sharing - Apple Support