Need some help configuring ASP.NET Core 3.1 auth

I am trying to setup ASP.NET Core 3.1 authentication, as per the article.

However, I am a little confused by the terminology and workflow.

What I want to happen is that when the app is hit, a controller method/action is hit (this just returns a View) and on that page, I have the authorise attribute. My understanding is that the authorise attribute is invoked before the body of the method (returning the view).

Once the user authenticates, the body of the method (the page) is returned.

I’m a bit confused by what the callback url and return url would be in this case?