From the My Verizon Home screen, navigate: Plan > Add-ons and apps.
Only the Account Owner or Manager can perform these steps; here's additional info on account roles.
From the Premium Products section, click Get Apple Music.
To continue, click Enroll in Apple Music on the preferred compatible line.
To continue, accept the Terms and Conditions then select Confirm.
Once Terms and Conditions are accepted, 'Add or opt out of Apple Music' appears with additional info. A confirmation text is also sent to the applicable mobile number with additional enrollment instructions.