if you mean the advertising area at the very top you can insert any html code you like (advertising widgets don’t support flash files). Just put the html/flash embed code of your flash object into the advert option field.
How can I ad an SWF to an advertising sidebar area? I see you mentioned that the ad widgets don’t support flash, so how can I accomplish this, what widget do I use and how do I reference to the SWF in the media? Appreciate your help – the JPEG ad I’m trying to swap for SWF is located here — http://chestermagazine.com/category/food-and-wine – top right, Village Square.