Hi Vicki,
Here's what you need to do:
Move the dashboard along with the dependencies (which includes universe, connections, query metadata, etc.) from the Test environment to the Production environment using promotion management tool.
Once the promotion job runs successfully and you have all the dashboards and its dependants migrated to the Production environment, simply open Information Design tool (IDT) and edit the connection to make it point to the Production DB server. You can do this by: Opening IDT >> Insert session >> Expand Connections >> Double-click on the required connection >> Click on Edit >> Specify the appropriate database details.
You may refer the following SCN article:
Hope this helps.
Regards,
Niraj