New to ASP/MVC... Question about authentication

So I'm completely new to ASP/MVC. Basically, I need to be able to create small site where the user logs in with network credentials that are validated against AD. I know how to do the AD validation part, but I do not know the proper way to authenticate the user for the web session with ASP. Can someone please give me a basic idea of how the authentication mechanism works here ?
 
Thanks,
Sam.