How do I announce to the community that a game demo (or version) is online and ready to be tested and reviewed?
There are many ways to do this, but here are just some different methods.
There are a couple Forums frequented by users of the OHRRPGCE, these are always a good place to ask for feedback on your game.
You could also discuss this sort of thing on the OHR IRC channel. You can find a list of channels and servers at the IRC Chat page.