Install the required graphics card(s) into your server, and power on the ESXi host.
Go to VCenter and find the ESXi host the card was installed in.
Click on Configure -> PCI Devices and Configure Passthrough
Select the GPUs and Audio Controller. The Audio Controller is not necessary, but I tend to use it anyway.
Reboot the host, and verify that the Status shows Available
Configure your Virtual Machine with the required resources, and select reserve all Memory
Got to VM Options, and select Advanced -> Configuration Parameters – Edit Configuration
Configure and add the following Key Value Pair
Power on the VM, Configure the OS and Graphics Card Drives, and pass thru should work as excepted.