This article explains how to add users to the Meta Business Manager

  1. Go to Business Settings
  2. Below Users, click People
  3. Click invite people
  4. Enter the email address of the person you want to add. Click Next.
  5. Select the type of access you want to assign. Click Next.
  6. Select the asset you want to assign and choose the type of access.
  7. Send Request. The person will receive an invitation to join the business portfolio via email.