1. Just type, for example /connect irc.afternet.org and hopefully you'll be connected.
2. When you do get connected, type /join #marp and you'll be talking to other people from MARP real-time.
You can also go here if you have a java browser(IE 4, Netscape 3 and better I guess) and chat that way. Follow the instructions, you'll join #help by default. Type /join #marp to join #marp. You can then close out #help.
There's a video game trivia game that occurs every saturday night at 10pm eastern, 0200 GMT Sunday, at the same said chat channel.