Step 1: Download the Client
Download and install the mIRC program on your computer. Open the program from the location it was installed to.

Step 2: Connection options
As most programs do, mIRC has an option menu. The option menu is where you will configure your connection details and other options.

Click the Connect tab, and enter your nickname, alt nick, full name, and email address. You don't need to use your real information.

Next click the Servers tab. Scroll through the list of networks untill you see Undernet. Double click on Undernet, then choose the server you wish to connect to, highlight and click "OK"

Step 3: Join #Family_Chat

Once connected to the server, there will be a channels box that will pop up, simply type #Family_Chat, and hit Ok