Firstly, there's no such thing as "an mIRC server". mIRC is a client for the IRC protocol which connects to IRC (not mIRC) servers. There are many kinds of IRC clients, including bots, and most of them are not "mIRC".
This brings me to my second point: this forum is for mIRC support, not other clients. We can't really help you configure a bot for your channel, though you might want to look into getting an "eggdrop" (or "windrop" under windows) bot. Keep in mind, if you run a bot, it needs to be running on *a* computer somewhere 24/7.. so unless you have a shell (might wanna look that up too) you'll still need to keep your machine on. Again, all of this is out of the scope of mIRC, so you may want to look elsewhere for support.