Although _pORKCHOPS said it, here it is again, a bit clearer:
First off visit the website,
https://qchat.rizon.net/Once you are there, enter your nickname in, which is usually your minecraft name, but can be anything you want also. But it's just easier if it's your name so that people will know and recognise you.
Then you enter the channel name. Opticraft's channel name is: #opticraft-smp
The password is blank or covered over, since you have the choice to enter your password later.
Now the last thing to do, the auth box. You leave it blank, I dunno what it does or means, but just leave it blank.
All that is left is to click connect.