Sixpack 1.2: how to log in two users?

Now for an *actual* noob question:

terminals 0C0-0C2 are defined in hercules, but I can only open a session and connect to CP through 0C0. 0C1 just sits at the Hercules banner.

I've heard the term directory, how does that interact with or substitute for VM's IOGEN? Where do I find either of these entities? -Or does this have nothing at all to do with that? 

A two-or-three-sentence primer on VM I/O targeted to an MVSer will probably kickstart me suitably. I know MVS sysgens but this seems to come at me a little bit sideways. I'll wager that at the end of the day it's more familiar than I think. 
I always secretly wanted to be a DOS/VM guy but none of my employers ever wanted to, er, "re-size" their existing MVS installation. At my very first shop we were bringing the systems in-house from a service bureau, and all the VM manuals had arrived, and I was burning through those when they changed their minds and I had to learn instead to support MVS/SP. Can't complain, it just would have been fun... -and retrospectively, the right call for a company of that size. IBM sales was just too darn good.