Once the new RDMs have been added to the virtual machine they will show up in the Windows Server 2012 R2 VM. If they do not show up automatically perform a rescan operation. Once visible it will show similar to the following.
Each of the newly added volumes will need the Drive Letters update. Right-click the Disk # and select Change Drive Letter and Paths.... to assign.
For this example drive E:\ and H:\ are assigned to Disk 3 and Disk 4.