Verifying my location with code sent by letter - I cannot find where or how to do this

I have looked everywhere on the Extranet and forums trying to work out how to verify my location with the code sent to me by letter but it is impossible to find where to add this in my property listing which has already gone live.  There is no where on the Extranet page which says or asks 'Confirm your location'.  Can you please explain how to do this as it is exceptionally frustrating for new hosts.