Locate the envelope marked as “Cisco Vmware vSphere Hypervisor 5.0” in the shipping box. Locate the card titled as “Right to Use Notification” in the envelope. Note down the Master serial number, which is the license activation key.
In the vSphere client, Navigate to Configuration > Software > Licensed Features , and click Edit Select Assign a new license key to this host. Click the button Enter Key... and type in the Master serial number noted in previous step. Click OK to close configuration dialogs and apply the license