The problem is you selected "StatusMessage.cshtml" which does not contain a cs file. Therefore, there is no "Areas" namespace in the code.
Try again but select Login or any Razor Page that has a cs file.
Or add a class to the project that has the following namespace to get past the compiler error.
namespace AuthenticationTutorial1.Areas.Identity.Pages.Account
{
public class MyClass
{
}
}