From the Dashboard, click on Phone Systems and select Music on Hold from the drop down.
Click on Add Music on Hold
Type the Description and Select the Audio File and click Add
Click on Apply Changes
From the Dashboard, click on Call Center and select Call Center Queues from the drop down.
In Show Queues Section, click on Action Button and select Settings from the drop down
Click on Call Routing Tab
Scroll down to Hold Settings Select the Hold Music you need.
Scroll down and click on Apply Changes