Administrators add users to Target by inviting them to join.
This video explains how to set up Target users and administrators.
After you add a user, the user receives an invitation email.
You will not see the new user listed on the Users page until the user logs in using his or her Adobe Marketing Cloud account and then logs in to Target Standard/Premium by clicking the Target card.
Add the user in the Target Classic interface, and then give the user the generated password.