Unless I'm missing something, you don't need to configure nothing from vSphere side, you should make sure your have correct DNS settings and open port between your KMS server and the machines that needs activation.
I believe that who told you to configure the vSphere to connect to the KMS server, is not talking about the Microsoft Key Management Service, but talking about Key Management Server that generate and store key need by the new vSphere encryption feature, see: Connect a vCenter Server System to a Key Management Server (KMS) (2147566) | VMware KB
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Richardson Porto
Senior Infrastructure Specialist
LinkedIn: http://linkedin.com/in/richardsonporto