Q. How can I make a server or client use Key Management Service (KMS)?

A. Use the slmgr.vbs script to pass the KMS key for your version of Windows then force an activation, as shown below. You'll note in my example that I don't have five servers activated to the KMS initially, but after I've set up another four, it activates.

C:>cd windowssystem32

 C:WindowsSystem32>cscript slmgr.vbs /ipk 489J6-VHDMP-X63PK-3K798-CPX3Y
 Microsoft (R) Windows Script Host Version 5.8
 Copyright (C) Microsoft Corporation. All rights reserved.

 Installed product key 489J6-VHDMP-X63PK-3K798-CPX3Y successfully.

 C:WindowsSystem32>cscript slmgr.vbs /ato
 Microsoft (R) Windows Script Host Version 5.8
 Copyright (C) Microsoft Corporation. All rights reserved.

 Activating Windows Server(R), ServerEnterprise edition (620e2b3d-09e7-42fd-802a-17a13652fe7a) ...
 Error: 0xC004F038 The software Licensing Service reported that the computer could not be activated. The count reported by your Key Management Service (KMS) is insufficient. Please contact your system administrator

After time has passed and four more servers have been configured:

C:WindowsSystem32>cscript slmgr.vbs /ato
 Microsoft (R) Windows Script Host Version 5.8
 Copyright (C) Microsoft Corporation. All rights reserved.

 Activating Windows Server(R), ServerEnterprise edition (620e2b3d-09e7-42fd-802a-17a13652fe7a) ...
Product activated successfully.