Use the Veritas Application Portal to invite test and development users to Velocity. It might be helpful to have a list of users and their email addresses ready before you begin. Then, in the Velocity Console, create a new role that lets the users have access to the database source so that they can create sandboxes from the database copies.
Alternatively, you can assign the database source to an existing role. Any sandbox users that are assigned to that role inherit permission to access the new database source.
After users are added to the Veritas Application Portal, they do not appear on the Users dialog until after they sign in to Velocity.