ASP.NET MVC Mixed Mode Authentication

I am using Visual Studio 2015 with MVC 5 and need to enable both Windows and Forms Authentication for the same application. I read that one approach is to have two applications: one has Windows Auth enabled; the other has Forms Auth (main application containing all pages).

If the user is authenticated through the Windows Auth site, their credentials are passed to the Forms Auth site; otherwise, they will have to enter their credentials.

I was looking for a way to do this. Will the Windows Auth app somehow send the username to the user only to the Forms Auth app, which will then assume if a name is provided to authenticate the user?

How do you do it? Thank.