If you want to run a PbP game here, put a post up in this forum (Looking for Players or Games) with the details and see if there is any interest. When you are ready, send a private message to one of the forum admins and they will set you up with a forum and give you full access to it. Adding players to your campaign is then just a matter of adding their forum username to the campaign group.
Also a couple of suggestions, it would be a good idea to add [OPEN] or [CLOSED] to the main post title so readers know quickly what they should be reading. Details such as basic setting and house rules will help people decide if a game is for them. Finally, there is no minimum number of players, if you get even a single bite, feel free to PM a forum admin and they will set everything up for you.
If you need help or have suggestions, you can post in Forum Help or Suggestions.