The URL in question: www.globalcw.net/shop

I need some assistance with this. The template I have used is a free template. I want to replace the white on my website where the custom banner (i made) appears.

The banner has GlobalCW.net in the image. I want to stretch my image right across from categories through to the right and side. If I am unable to do this, then I want the white replaced with a colour of my choice.

Can anyone please advise how to fix.

Regards