If you want people to call in to your station, they should call to the VoIP software (I know some people used Skype for this), and then RadioBOSS/Virtual audio cable (VAC) does all the work to broadcast it to the other listeners.
It's also not required to have RB on the server, you can use it from your studio/home computer, like this
[STUDIO] --> [Stream host] --...>>> Listeners
[STUDIO] is your computer where you have RadioBOSS, VoIP, VAC etc installed;
[Stream host] is a hosting solution which provides bandwidth for listeners (loudcaster.com for example)