Once you have granted access to your Private Security Portal for a user, that user can go directly to your Public Security Portal URL (for example security.safebase.io) and click on the Access Private Portal button in the top-right corner of the page to login to your Private Security Portal.
Instead of having to remember a unique link to the Private Security Portal. They will now only have to remember the URL of your Public Security Portal. Once they click on Access Private Portal, they are prompted to enter in their email address. If the email matches a user that has been granted access, they will receive a magic link in their inbox to access the Private Security Portal.