How do I add family members to Apple Music I already bough

Set up Family Sharing - https://support.apple.com/HT201088 -

"Invite people to join your family

After you send the invitation, you can check its status under the person's name in Settings > iCloud > Family on your iOS device. On your Mac, go to Apple menu > System Preferences, click iCloud, and select Manage Family. Then select that person's name to see the status of the invitation.

If you need to resend the invitation, select Resend Invitation."

See this support article which includes instructions for inviting your Family Sharing members to join:

Get an Apple Music Family subscription - Apple Support

Cheers,

GB

Did you even look at the link? It is not just about the subscription. It is about how to invite people. I know you already had the subscription.

GB