The default text under "What IS YourSiteName?" goes like this:
You'll want to customize this page. Read the instructions at http://www.livejournal.com/doc/server/lj.customize.index.html for help.
Just WHERE IS that text so it can be changed? The help at that URL is not very informative. I've searched and searched and I just can't find it, so I'm obviously looking in all the wrong places.