I'm afraid you can't just begin roleplaying without any set process; there are rules and guidelines to be followed. If you have any questions, don't hesitate to ask one of the section regulars, through VMs or through the Roleplaying Tavern.
Moving this over to the Canon Sign-Ups section. For roleplays here, you have to start with a sign-ups thread (where things like the storyline and rules are listed) and then you can move onto an in-character thread where you can begin roleplaying. Like Commissioner Gordeith said, ask if you have questions! We'll be more than happy to help you out.