Although theoretically possible in vSphere 6.0 VM secure boot support only officially supported with vSphere 6.5. Interesting thing with 6.5 is the range of improvements made in the security space with the hypervisor. Been good too that VMware have been listening to the user community in simplifying the adoption of a lot of these features.
An example being VM secure boot support which is easy to setup.
I) Requires EFI firmware support
II) Works for Windows and Linux virtual machines
To setup simply:
i) edit your virtual machine properties
ii) Choose VM Options tab
iii) Make sure EFI is choosen under the Choose which firmware should be used to boot the virtual machine
iv) Tick the tick box beside Secure Boot (EFI boot only) and ok
And your done