How do I load shared music onto my son's iPhone?

I have home sharing and family sharing active on all devices. When my son signs into iTunes (v 12) on our iMac (Yosemite), he can see my music library. However, we cannot figure out how to put the music onto his iPhone (iOS 8). In other words, he can play my shared music library through iTunes on the iMac, but it seems he has no ability to copy my music to his device. Note that we are set up as two different users on my iMac. At one time, I was logged in as the user, and we sync'd to his phone to my account. We could copy music to his phone when that was the arrangement. I later set up his own user account on the iMac and made it the primary account for sync'g the iPhone. That was when I ran into this problem. Despite the sharing settings, he can no longer copy my music if he is logged into his account. With the understanding that it is preferable for him to be able to sync while logged into his own user account, does anyone know if it possible using iTunes 12 or some other program? If so, I would appreciate any guidance. Thanks.