Getting started is simple...
Visit the iTunes App Store and download Truphone to your PC or Mac. Next time you sync, Truphone will appear on your iPod Touch. Or, alternatively, you can choose to download Truphone straight to your iPod Touch by accessing the App Store directly from your iPod Touch.
Follow the simple steps on your iPod Touch to install Truphone. It takes seconds.
Add all your Truphone and Google Talk friends to your TruFriends contacts (this can be done manually or by importing them from your iPod Touch contacts).
Plug in your microphone headset, which you can purchase here
To start making calls, whenever you are in Wi-Fi.