Built ASP.NET Application in Visual Studio - How Move it to IIS Express?

Been scouring web, this seems like a very simple thing to do…I have done a lot of PHP deployments, but ASP.NET is killing me…

I built ASP.NET app in Visual Studio. I can run it from the IIS Express button. Not sure what it does, sticks in on a new port. Anyway, I want to take this app and put it under IIS Express so I can run it just from localhost in browser. I know how to Publish, and can create the publish folder under bin. All very simple. But, in the directions, it says to copy all those files to the web site – I’ve done that, into the document root. But there is no htm, html, .aspx, etc, etc file. How do I run this app that I copied over?

For example, my app is HelloWorld. There are EXE, DLL, PDB, JSON, and other files in the publish folder. There is a wwwroot folder with CSS and other stuff. What do I need to do to put this under IIS Express and run it as /localhost/HelloWorld or whatever?

I am missing something very elementary here. I feel stupid, because I’ve done some very complex sites with PHP, JS, MySQL, etc, etc…

Thanks…