First, you'll need do download and install mIRC.
If you're not already on the options screen, click on it's icon.
Your options screen will look like this:
The nickname you specify will be overridden by the settings on IRCRelay.
Your email will be in the format of ircrelayusername_ircnetwork@ircrelay.com. mIRC uses this as your user name to authenticate with IRCRelay.
Click on the "Server" folder of "Connect" to view the Server List
Click "Add" to add a new server.
The Edit Server screen will look like this:
The Name of the Network is up to you! Since we're setting up a freenode network, I'm going to call mine IRCRelay Freenode.
Your server and port will match the screenshot.
Your group is optional, but will allow you to group your IRCRelay connections.
Your password is the password you signed up for IRCRelay with.
That's it for configuration. Click "OK". To return to the Server List. Click "OK" to leave the Options screen.
Last but not least, connect to your server by clicking on the Connect icon.
If you're having trouble, please visit the support page.