Import VirtualBox Appliance
Open VirtualBox
Select Import Appliances under the File menu
Click the folder icon next to the text field and navigate to the .ova file that you downloaded. Click the "Continue" to proceed.
A window showing information about the virtual machine will pop up. Click the "Import" button to start importing the virtual machine. It will take a few minutes.
When done you should see the virtual machine in the list of virtual machines that VirtualBox knows about on your machine. You start the machine by either double-clicking in the VM entry in the list or by selecting the VM and then clicking the green start Arrow.