Now it's possibile to add your mIRC nicks to Trillian! Below you'll find a picture of my own Trillian/Irc connection. (Visual aides are sometimes best.) I included a picture of where to add in your identity pass upon connection. Any questions? Just ask.
If the pic is killing your F-List let me know. I'll slap it under a cut... I'm to tired right now to look up or think about the code for it.