[url]https://forum.atlas-games.com/t/instructions-for-gms/1597/1] is instructions for GMs, the very first post tells you how to apply to get a subforum for your game and the very important instruction on getting your players to change their settings so they can post to games.
If you have the inclination to run a play by post game, put an announcement in the looking for players area, there's always people looking for games. A few will drop out quickly, so always aim to fill your game so there's enough after the inevitable early losses.
As for looking for a game - they seem to come and go in batches, sometimes there's a load of game with spaces and sometimes they're all filled or dormant. If you know what you want, run it.