Running RPs on DW - How To?

[trouble]

So, I know that people run journal-based games on DW, LJ, IJ, and JF. I've run online RPGs before, but always in a forum-based setting, where we'd declare particular forums a "space" that people were in.

So, a typical forum would look like this:

CHANTRY:
Library:
Lab:
Outside:

COFFEE SHOP:

Tanya's House:

Stuff like that.

So... how do people run RPGs on journal based systems? Do they set up threads? Do they have one main community? I know people use their journals for stuff, but I don't understand!

Halp?