You have to use the vB code thingy, I think it follows this format, minus the second L's in "URL":
[URLL=site address]Text Displayed in link[/URLL]
Just raplace site address with the address of your site and the Text thing with what you want the link to say, and you'll get this:
My Logo Site
Sorry, that was a cheap plug for my site.
Once you get the link in there I'll put a link to it on my site, since I like your logos a lot.