Once you have spun up a new site, you can add more people to the site's dashboard. Use the person's berkeley.edu email address if possible. If the person has not already signed up at Pantheon, Pantheon will send an email inviting them to join.
Anyone you add to the site dashboard will be added as a Team Member and be able to perform operations on the site via the Pantheon dashboard.
Web Platform Services strongly recommends using CalNet authentication for all sites. If you are working with a third-party vendor or collaborator who needs to be able to log in to your site, they can get an Affiliate or Guest account. Once the account is set up, they will be able to log in using CalNet authentication.