I want to say there is a simple way to do it with smf, but it's been a while since I've been behind the scenes on a smf board. I seem to remember being able to replace a file in regards to the images the skin uses, but you would have to do that through a ftp, that option might have been due to using a custom skin as well. I would suggest thumbing through the admin cp before modifying any code, simply because it would be less of a headache.
With a quick search I found this, and it sounds familiar, "or you could just go to admin then current theme, and then click themes and settings and put the HTTP code in (logo image url)...this will take the place of your forum name thats so plain..."