I’ve been using ZNC on one of my VPS’s for quite some time, connecting from XChat on Ubuntu GNOME desktop. I also have a Mac, so decided to also use that to connect to IRC. Since there is no XChat client for Mac, I tried Pidgin, they don’t have a Mac client either, but there is a client based on their libpurple called Adium.
Add a new account by clicking Preferences under Aduim on the top menubar. Go to Accounts and click the plus sign. Select IRC.
Enter your Nickname, Server (ip or hostname of the machine running ZNC), and enter your ZNC username and password in the Server password in the following format username:password. If ZNC is running on another port than 6667 go to the Options tab and enter the correct port.
You should now be able to connect successfully to your ZNC bouncer through Adium.