You can write your own bot in most languages. However, if this is your question, you might not want to use one - what purpose will you channel have?
For instance, many factions have their own channel with a chain bot. Or my IRC channel, which has a travel helper and general purpose bot, etc. In that way, each bot fills a role. If you're just looking to chat, you don't really need a bot. :)
Setting up a channel is easy: type "/join #desiredchannel" and then type "/msg chanserv help register" and follow the instructions it prints.
I'd also suggest (obviously and if not already, and on top of what swat so nicely explained), that you get a good IRC client. That will make it easier for you to manage things, and well the 'simplest' bot would also need a client to run on (This is UTA, made by PMV, linked at the bottom of my post)
The bot I am reffering to needs mIRC to run on, but ofcourse there are many other good clients usefull for IRC like Hexchat & Icechat.
Thank you. I'm thinking about a bot for the company I'm in because it has monthly prizes, and everything like like, so it would make it easier for the director to get on IRC it select a random person out of the company list and that's who wins the prize. And also display a player eff, how much they are making the company and the company stats, such as how much was made thay day. And even have a bot set a training routine for players to be trained.. This is probably a really stupid idea but thought it would be good