Looking to activate your shiny new Windows 10 clients with your KMS? This is what you need to do.
1) Install following update on your KMS host: https://support.microsoft.com/en-us/kb/3058168 (Select the OS of your KMS. Reboot is required.)
2) While we are waiting for Windows Server 2016, MS has created an unique KMS key for the use of activating Windows 10 clients with a Server 2012 R2 key. Browsing your licensing site, you will find a key named like this: Windows Srv 2012R2 DataCtr/Std KMS for Windows 10
3) Install the new key with the usual command: slmgr.vbs /ipk NEWKEYGOESHERE
4) Activate the key using: slmgr.vbs /ato
5) Lean back and watch your W10 clients being activated by your KMS.