So where do I go to download the IRC and do I have to have certain applications for the computer to run it?

There are several IRC applications, one of the most commonly used ones is mIRC.

You'll have to create the address for the Darkmyst server before you're able to join the right place, the address is irc.darkmyst.org. Add it to your server list and you're good to go -- #EfU is the channel.