Forum:How do you change the main picture of a wiki?

Hi. I am an admin of the Khan Wars wiki. I can make edits to the side-bar, the main page, and do all the other things that admins do. However, I am relatively new to this, and I can't figure out how to change the main picture. You know, the one that goes over the side-bar on the left. I have a much better one in mind. Thanks. -X52495nos4a2 20:34, May 25, 2010 (UTC)
 * Read the help page about the logo. 20:37, May 25, 2010 (UTC)