iPod 4th Gen and bluetooth

Hi i have an old bluetooth headset that i used with my my phone a while back and have now paired it with my iPod but i'm not sure how to get it to use the headset for audio and microphone. i want to use skype through my iPod rather than my computer as the computer's mic is rubbish and i can't link bluetooth to my comp and so i was wondering is it just simply a case of i can't use the headset for this purpose or is there some setting i've missed?

cheers