If you meet the eligibility requirements, the Account Owner or Account Manager can follow these steps to sign your line up for Apple Music:

• Visit Verizon's webpage on Apple Music on your computer or smartphone's browser.
• You can also enroll from the My Verizon app:
  
  1. Tap Menu. Then tap Account and Add-Ons.
  2. Select the line you want to enroll in the Apple Music promotion, tap the Entertainment tab and then tap View for offer details.
  3. To continue, accept the Terms and Conditions by selecting the check box, then tap Get Apple Music.
  4. To finalize your enrollment in the trial, tap Confirm and then Got it.
  5. Each line will get a free text message within 24 hours. Tap the link in the text to either download Apple Music on Android or to open Apple Music on iPhone.

See Apple Music FAQs