I am adding users to the portal, do they get an automatic email inviting them to join once I have added the individual as a user?

Yes, each time you add a user to the system, they should receive an email (at the e-mail address that was entered for them) inviting them to set up their password and use the system. Often, these emails can land in your spam folder, so if you do not receive an email, please check the spam folder.