Try to convince your local emacs administrator to put irchat.el to a globally accessible elisp directory and to add this info to the info tree. No modifications are needed in irchat.el itself, as long as the irc port is 6667 as it usually is and the server is local. If your server uses different irc port or you use non local irc server then you have to set them by setting environment variables IRCPORT and/or IRCSERVER.
You need add line containing following to your .emacs, that way
can start irchat by issuing command M-x irchat.
(autoload 'irchat "irchat" "GNUemacs IRC client." t)
If you are not happy with the way irchat.el is when shipped, you need to
have a small piece of code for yourself for setting some variables that
control irchat the way you want them to be. You may place them in your
.emacs or in an other file to be loaded before starting irchat itself.
See the section called "Customizing irchat.el" for info on the
customization possibilities.