The ballroom is in house one on floor one. You can get there via going back up the pathway in the Slaughterhouse to house two, and from there to house one. It's a bit of a walk, but fairly easy to get there from your current location, and no worries! Feel free to IM one of the mods if you need help, that's what we're here for!

Here is a link to the setting post start page: http://allthekeys.dreamwidth.org/493.html