Before we go on please make sure that you have the following:

Data Subscription on your Network with Support for Data Access from Java Apps.
This could either be a GPRS Connection or a Wap connection. Whatever, it is, it is better to have a Traffic based Subscription rather than a Time based Subscription as chatting involves less traffic & more time. Generally, GPRS is billed Traffic wise whilst Wap is billed Time wise. Contact your Service Provider for more information.

A phone with Java MIDP Support with Data Service Access & OTA Java App Installation & a max jar size of about 30-40 kB or more.
Almost all Java supported phones fill this criteria. OTA Java App installation support is not mandate but, this document will guide only through OTA installation as other ways of installation are rather complicated for an average phone user & Installation Procedures differ from Phone to Phone. So, if you don't have OTA, but have Java MIDP support please contact your phone vendor for more info.

Many free mobile IRC clients are available for download. Namely, jmIRC and WLIRC. Here, I will teach you how to download jmIRC.
Simply point your mobile browser to the following URL and follow the instructions for Download.

http://jmirc.sourceforge.net/jmIrc.jad

Your phone may display a warning, select continue. For more info refer your phone user guide.

Now your phone may prompt whether you want to run jmIRC now or later. Select the command to run now. If your phone doesn't prompt you, follow the procedure that you usually follow to run Apps & run jmIRC. Refer your phone manual for more info.

Now press the Options button. Select Profiles & then Add New. Sometimes jmIRC may directly prompt you with a settings dialog. Either way you will get the same dialog. Fill in the dialog as follows.

Profile Name: Any name that makes sense.

Nick: Your preferred nick.

Alternative Nick: Nick that'll be used incase the first nick isn't available.

IRC Server: Any IRC server address

IRC Server Port: Server port, usually,6667

Channels: Any channel that you want to be joined on connection

User Name: This field is not required here. You may learn all about these in the Standard IRC guide.

Real Name: Your Real Name. It could be fake as well!

Server Password: Your nick password if you have a registered nick. Read more about these in the IRC hand-book.

Press Save.

Press Connect.

Your may phone display a warning saying that this app is trying to access data service. Select Ask Once Per App. And validate your choice. Refer your phone manual for more info. If your phone doesn't display a warning and connects, no problem. If it doesn't display a warning & you get a Socket Create error follow your Phone Manual & allowing Data Service access to Java Apps.

There you go, now you can chat on IRC with your mobile

This simple guide has been made generic so, refer your Phone Manual for precise information. The terms used here may differ from the actual terms that may appear on your phone.

For further info on jmIRC goto, http://sourceforge.net/projects/jmirc/

can you do this if you use a program like opera mini to connect to the internet?