You need the button code as well as the image code. Influenza has just posted an amazing guide on it. Go check it out my clicking here.http://sythe.org/showthread.php?t=694464
Yeah, if you follow that guide, you should have a Donate button that's functional in no time, http://sythe.org/showthread.php?t=694464.
Let me know if you have any questions/concerns.