1. First you go to the virtual machine menu then select Details
2. Next select the Hard Disks menu and Edit
3. Resize disk
4. Go to VM and check the current condition (open console or RDP), open Computer Management
6. go to disk management, and you can see Unallocated disk
7. Expand disk with disk available or create new disk
*If you want to expand then right click on system C and click extend
*If you want a new partition, right-click on unallocated and select new simple volume.
here is an example after expanding / extending the disc :
