Inserting top banner image in mid-column in Wordpress

I want to add a permanent banner ad at the very top of the middle column in my 3 column Wordpress-based blog. The middle column contains the blog posts. I would like for it to be easy to turn the banner on or off with the design of the page adjusting accordingly. FYI, the banner image file is externally hosted. ## Deliverables The website that is to be edited is [login to view URL], which is a men's fashion blog. The banner size will be 558x100 pixels. In the pictures attached I have illustrated how I want the banner placed. The banner should also be placed on top of all other content in the middle column. The top of the banner should be aligned with top of the widget boxes in the left and right columns.