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.