How to set up pc to pc free calling on yahoo instant messenger 9?

I am confused by what you mean by set up. PC to PC calling is included nothing to set up. Send and IM to the person you want to talk to and then click the call icon that looks like a phone in the upper left of the pm window to do the pc to pc calling. Now PC to phone calling called phone out is not free. Could you give some more details as to the problems you are having and the steps you have taken? It is best to use a headset which will eliminate echo if both parties use a headset. Otherwise you would need separate speakers to hear and a mic to talk.