Adding disk space after extension in Windows Server 2008 R2

After disk space is added to a server in a panel, do the following to make it usable by Windows Server 2008 R2.

Open "Computer Management".
"Start Menu" - "Administrative Tools" - "Computer Management":

Open "Disk Management".

In the left panel, select "Disk Management" in Storage folder. Press F5 to refresh the window and see the unallocated area. In the bottom right panel, you will see an Unallocated space (40 GB in the below example):

Click "Extend Volume".

Select a volume to be extended and right-click on it. In a menu that opens, select "Extend Volume":

"Extend Volume Wizard" will open:

Select the size of the unallocated space you want to allocate (in most cases, you should select all available space). Click "Next":

Done. Verify that no unallocated space is shown in "Computer Manager":

and that Computer window displays the updated disk size: