I don't have a link on hand, but Googling "irc tutorial" should give you lots of results. IRC is mostly a command-line style interface. Presuming you're using Pidgin, XChat, or something else that has a GUI for accounts, and you're already connected, just type
/join #channel-name
a '/' at the beginning of a line denotes an IRC command

EDIT: #maemo's a pretty friendly place, but you'll probably want to read up on IRC usage and etiquette before you head out into that area of the Internet, as some people/channels don't take kindly to ignorance, just because they're jerks, and there are plenty of unintentional faux pas that are easy to commit.