Hi @Jaco Pretorius,
Regarding how to add a Microsoft login to a web application, Microsoft provides detailed steps in the document:
Quickstart: Add sign-in with Microsoft to a web app
Enabling Microsoft Authentication
If you want to use Windows Authentication, you need to disable Anonymous Authentication and enable Windows Authentication in IIS.
How to enable Windows authentication for a Web site, Web application, or Web service
Best regards,
Lan Huang
If the answer is the right solution, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.