Welcome to La Scène, our quick IC chat! The way it works is basically built on everyone's imagination. One person picks something like the setting or a particular situation to place everyone else in for the day or time frame they're using this room, and everyone else builds on it from there, interactiing with the given environment or scenario.
To give an example, let's say the setting is a beach carnival. Someone can come in and introduce another element to the setting, like a pickpoketer, and others can react and interact with these elements of the room as they come in.
Hopefully that makes more sense, but basically this is our room to play around and gather everyone in one particular setting/situation all at once. It's just something to have fun with and practice being IC with. The setting can and should change with the people in the room, so make this what you want to make it!