Adding a Image under the Menu

Hi Guys

I am using the theme Trizzy and I am trying to place an image directly under the menu, so the top of the image is sitting directly on the bottom of the menu – The image will be static

I have tried adding the image into the header.php but it 1 – leaves a big gap and 2 – doesn’t go site wide which I would like it to do as well, and I though by adding to the header.pho it would automatically go site wide

My site is http://www.curveboardsports.co.uk

I look forward to hearing back from you

Jake