I need to record an after hours message using our Cisco Call Manager. I think I need to be in Cisco Unified CM Administration

Next Monday is a holiday and I need to record a greeting message that specifics we are "Closed due to President's day".
In the past we used the Cisco Call Manager and a specific extension was called. Upon picking up the call, our receptionist was able to record a fresh greeting that was saved in .wav format . I do not seem to be able to recall exactly how to do it. The network admin that normally does this is out on PTO and I am looking for advice. I am logged into the Cisco Unified CM Administration, but not sure where to go from here. I assume I need to go to the VOICE MAIL tab, but could use some advice. If anyone has an idea of where I need to go, I would appreciate it. Thanks