If you are using Single Sign On in your Folio instance then you have the ability to make SSO the only Sign In option, meaning that when users try and log in they will no longer be able to do so using a username and password:
To turn this feature on, click on the gearwheel in the top-right of the screen to go to Folios Admin screen, then select Sign On and Security:
Then click edit and tick the box labelled Restrict login to use Single Sign On only:
Note: If you have Lite Users who are external to your Organisation and who need to Sign In to Folio. Restricting Login in to Single Sign On only will lock them out of Folio as they will not be able to use their email address and password to Sign In.