If you don't have a "real" IRC client, mibbit is one of the easiest web based clients I've ever used.
Goto: Mibbit.com - Easy and fast Webchat
Click the "launch mibbit webchat" button
Stuff will happen and a little white box will appear
Click on the server link and type in "irc.stratics.com"
Type in whatever nickname you want
In the room field type in #mcb - don't forget the # sign
Hit the connect button
That's all there is to it.