All you need to do is go to the control panel, at the top right of each page. Then scroll down to your signature and click on the small picture icon "insert photo", then insert the image url (you can upload/insert the pic to any one of your posts and then copy the image url, for some reason the signature box will only accept an url). To make a pic like mine just cut an image into a long rectangle, mine is about 1200 x 60 pixels, then select the text tool and type in your info, or you can just open a "new" blank picture in your picture software and select an appropriate image size (banner) or cut down a full image, then type in your info.
Just to be sure I went ahead and followed my directions with the clouds from your profile photo and signature info. Here is the product, you can just upload it from here if you like it (right click-copy image location).