I'm trying to replace the default yougrids logo with my own. I'm new to Joomla, and from what I've been able to gather I do this through editing a CSS file. Can someone point me to the right css file? And then is it as simple as changing the filename of the default logo to the one that I want to use? And do I need to put this .png file in a specific folder? It is already in my joomla media manager. Thanks.