I also can't figure it out. I still have some window that appears on the side and I can't figure out how to completely get rid of it (from my experiments with multitasking while I was reading the documentation, or at least some website describing it). I don't know if that's intended but I have no idea how to use it, so don't.

I had an easier time learning Xmonad back in the day, which might say something about Apple's UI design these days.