Full screen image on the home page

Firstly, I just love the theme. My problem is that I want to make the image on the home page full screen (and responsive at the same time). At the moment, I have set the layout to “Fluid”, so the top nav bar runs the whole way across the screen. However, the home page image / slider is boxed. I have tried increasing the size of the image, but it doesn’t do anything. Can anyone help please?