How I create a login controller? Codeigniter

I'm having some troubles with codeigniter and the MVC model. In my webpage I have a main controller with functions that handles the usual navigation menu with different views home page,about,support... but I have a login view.

1. I'm not sure if this separation is correct or I should create a controller for each view.
2. How do I call the login controller, I'm using base_url('main/myView/'); to call the functions inside the main controller, but if I call the login controller base_url('login/foo'); it does not work.

I'm new to codeigniter and I read their tutorial but I still not sure when should I create a new controller.

Thanks