This video tutorial from gogeeks shows how to install mIRC application on Mac OS X operating system.
For this you will need Darwine, download it from here:http://www.kronenberg.org/darwine/
and mIRC installer which can be downloaded from here: http://www.mirc.com/get.html.
Once both programs are installed, open Darwine.
Drag Darwine to Applications folder, then drag Trix there too.
Close and unmount Darwine. Now click Applications from Desktop dock menu and select WineHelper.
Process Window will appear on your Desktop. Click Applications from top menu and select Open. Now browse for the application you want to run - mIRC.
mIRC setup window will open. Install the application.
To test it, click Applications-Open-Program Files-Mirc-mirc.exe-Open.
Mirc will start. You'll need to register or enter your account information to use the program.