First, you will have to enable registration of protocol web handlers from different domains.
- Enter about:config in the location bar and press Enter to access the advanced preferences.
- Look for gecko.handlerService.allowRegisterFromDifferentHost and double click it to set it to true.
Now click in the link below to add Mibbit as an irc: links handler.
You will be prompted with a confirmation info bar. Press Add Application.
