Enter whatever name you want under “Nickname.” Check the “I have a password” box and enter this website without the https:// or .com as the password (no spaces, all lowercase). “Channel” should be #hello. Finally, click the “Start…” button.
Anything you type can be read by everyone in the channel.
For more information about IRC, check out the Debian 9 AMI IRC Server with IRC Bouncer article.