Just be sure to mind your alignment, as a Warlock and Hellfire Warlock. People will take it quite badly if you start causing general havoc. Similarly, actions have consequences, and stupid actions tend to have bad consequences (the Halfling Druid got his dinosaurs killed through some bad orders/tactics and evil dice).
As for getting the program up and running, when you open it up you'll see some tabs along the top. Open the Game Server tab and select the Browse Servers option. A window will open, showing you the active servers. If OpenRPG Dev II is up, select it and hit the Connect button. (If Dev II isn't up, then select Blackstar Games Server and Connect to it.)
Once connected, type "/name" followed by your desired screen name. I'll be easily identified, since my name is the same on EnWorld and OpenRPG.
We meet at 7 PM Pacific (currently GMT-7).