Hello there! I'm StringTheorist, the RPG-X XO. First off, glad you're enjoying being with us here so far! Now to answer your questions:
1: Aside from SRP (Serial Roleplay) episodes, the best way to know when a one-off is happening or even gather up a group to start one is the TLO Discord server. I'll add a link [Here] when I get a chance or someone below could provide it.
2: For SRPs, there is usually a thread labelled Crew Roster or Applications to apply for a spot on the roster. Take a look at Daedalus and Full Circle in the RPG-X Sub-Forum!
If you have any questions, please ask away. I have an open-door policy, and odds are there's usually someone around to answer any questions. Welcome to TLO!