Here is an example setup:
(setq erc-server "irc.freenode.net" erc-port 6667 erc-nick "your-nick" erc-user-full-name user-full-name erc-email-userid "userid" ; for when ident is not activated erc-prompt-for-password nil) ; OPN doesn't require passwords
To start ERC, use M-x erc RET. This will prompt you for server, port, nick, and password, and it will use the values of the variables above as defaults. Then just punch the required amount of RETs.
The ERC developers hang out at both the #emacs and #erc channels. #emacs is for general chat about Emacs, and #erc is ERC-specific.