SSO/Office365

How to use Office 365 as login provider instead of Active Directory

You need to create an Enterprise application

Click New application
Click Create your own application
Enter a name
Choose Integrate any other application you don't find in the gallery (Non-gallery)
Click Create (This will also create an App registration)
Find Properties for the Enterprise application you just created
Set User assignment required? and Visible to users? to false
Click Save
Click Single sign-on
Click SAML