Update SSO docs - auto assign

docs/enterprise/sso-self-hosted.mdx

@@ -35,6 +35,10 @@ After authenticating through your IdP, Briefer will use the authenticated user's
 
 Once you remove users from your IdP, they will no longer be able to log in to Briefer.
 
-<Note>
-  If you need to automatically create users in Briefer when they log in for the first time, please let us know. This is a new feature that we'd love to improve based on your feedback.
-</Note>
+## Automatically creating users
+
+If you want to automatically create users in Briefer when they log in for the first time, you should enable your workspace's "Auto-assign users from SSO" setting within the settings page.
+
+When this option is enabled, Briefer will automatically add the user to that workspace when they log in for the first time.
+
+<Note>**Existing** users will not be automatically added to the workspace when this setting is enabled.</Note>