To record an IVR greeting sound file:

• Navigate to 'Settings: Access Codes' and make sure that '*301' is set  under 'AA Greetings'
• Dial '*301' from your extension and speak into the microphone after the tone
• The recorded sound file should be saved under 'greeting-$DATE.gsm' name
• Edit the IVR and select 'greeting-$DATE.gsm' under 'Greeting' option
• Click 'Save'
  

Now every call that comes into this IVR will play your cutom greeting message