Andrew, MOH is not part of the Cisco 7960 unless you are part of a corporate environment using call manager.
If not you need to ensure your VoIP service provider has a MOH server.
Have a search of the internet, there are some independent MOH providers. You then need to point the Cisco to that server.
My personal situation is that I am considering changing the Cisco as it is a super phone but not really designed for a single point user.
There are more friendly phones that allow the individual to change configs