First, Download and install XChat 2 at this link.

Once you have done this, start it up and you will be confronted with a screen similar to this:

Enter all the details you need in the top 5 boxes. Click on "Add" type "FSMod" in the new box that appears and hit enter.  Now select "FSMod" and click "Edit".

You will now see this screen:

Simply enter everything I have there into the correct boxes(Hit "Enter" after you finish typing in the server name, or it won't save).  Make sure to check the "Auto Connect to this Network at startup" box.

Now, return to your main window, check the "Skip network list on startup", close XChat and turn it on again.

This was a quick 5 minute "Just the essential basics" guide.  I may expand on it if people ask me to.  Any questions on any other features, or if you feel something could use a bit more explaining, feel free to post here, ask me on IRC (if you get that far) or hit me up on XFire at "Gwynzer"

EDIT: This is untested, but it may be possible for you to just Install the Program then click the "IRC" link at the top, though I cannot guarantee this will work.