How do I use VOIP on livebox?

I have the adsl working fine etc, but I plugged in a confirmed working pstn phone into the spare rj11 socket and it doesn't work, no ringing tone when i call the 0203 that says is working and if i try and call out there is no tone and does not work.

Orange Broadband Talk Status 2
Talk service Phone Number 0203XXXXXXX

I only got unlimited last month and obviously I want to take advantage of the free calls...

Any ideas?

Just to elaborate, the adapter provided is plugged in, the telephone light is on so I don't understand...