Nettalk is an IRC client, freeware and really recommandable for IRC beginners. The screens in this guide are in German so far, but I am going to update them soon.
Nettalk can be downloaded here. After opening the setup.exe you start with the installation process
Installation:
Choose your language and click on "OK".
Click on "Next".
Click on "Next", maybe you want to change the path.
Here you can change some settings, but default ones are also okay. Click on "Next" when you are done.
Check the settings and click on "Install".
Click on "Finish".
After installing Nettalk you need to open it first.
Configuration:
Click on the first icon in the bar to add a new server.
Enter the following data:
Server: irc.onlinegamesnet.net
Enable "Use UTF-8 for messages" and click on "Next".
Enter the following data:
Nickname: your nick, e.g. Tester
Password: leave it empty
User-ID: your nick, e.g. Tester
Real name: your nick, e.g. Tester
Serverpassword: only necessary when you got an an auth account (you can create an account here: http://www.onlinegamesnet.net/authRegister.php)
If you got an auth account, you need to enter your data in form account:password. If my account is Tester and my password mudi5osu, I need to put Tester:mudi5osu into this field.
Click on "Next". Enter the channels you want to join automatically, normally you just need #tera.com, but you also can add other channels.
In my case I enter:
/join #tera.com
Click on "Complete" to connect to the server. You will automatically join the English TERA channel and can now chat with us! 
