In the Oracle VM VirtualBox Manager, highlight the Machine to clone (it should be shutdown) and select the menu icon that appears to the right of that selection. By default "Details" is selected. Choose "Snapshots" and click Clone in the icon bar that appears at the top of the right hand section of the VirtualBox Manager window.

In the example below, the screenshots show the steps necessary to clone a Windows 2012 VM running SQL Server (with the intention to use the clone to test SQL Replication... i.e. both VMs will need to be started up and visible on the same network)...

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