These are basics of MVC5. You may wanna take a look at the at some documentation around that.
To give you a bit more specific with your issue. With your controller, if you have it named
HomeController with an
Index, by default, the controller will look for the view named
Index in the
/Views/Home folder. The
/Views/Home folder and the
Index view in that folder is "automatically" hooked up because your controller name is
Home. So by default it's looking for that
Home folder in the Views folder and displaying the
ActionResults name as a view name.