Portfolio slider and Header

I would like to extend my slider to be behind the menu and extends across the width of the screen and to the top of the screen, as you have here – http://themes.skywarriorthemes.com/?theme=Game-Addict

But I am running into an issue where there is a header graphic that appears behind the menu and the slider is just below that vertically.

Can you help me to figure out how to expand the slider? I attempted the customizations through the WP-slider tool and yet it won’t go over the header banner.