I’d suggest asking for help on a forum more suited for bot development (maybe Hawkee http://www.hawkee.com/), since this doesn’t really pertain to Twitch’s SDK or API.
The system you want is quite simple if you use a text file. Just have two commands that add and read/remove lines from a text file. There’s probably some mIRC tutorials you can Google on reading and writing to text files from mIRC too, since it seems you’re a beginner.