As far as I know, you should be able to replace it by simply uploading an image of the same size to your theme_images subdirectory.
However, at this point things get complicated. When you publish, Wizard will replace the image with the original.
So, every time you edit, you will need to upload that image again.
(When I say "as far as I know", it is because I don't really use the Wizard. I know changes have been made since I did a test page to see if this could be done. Also, there is more than one version of the Wizard.)
many thanks for that.Yes you are correct it is that image. We have our own logo that we want to put there. I think I have got it. Maybe I will leave that bit to last,if it needs to be done each time I edit, as I am editing this site madly at the moment, almost on a daily basis (new venture)