What Len said.
For private roleplays, you have to ask if anyone wants to join in your signature or something. Then when they ask you for more details, you PM them on what it's about and if they accept you give the applications and say denied or accept.
And after a while you start the private roleplay in the 'Private Roleplay' forum, but only the accepted people can post in it.
I'm really bad at explaining at times. .-.