Navigate to customerconnect.vmware.com and sign in. If you only have a free account, you will see limited downloads. You need an entitled vSAN license.
Click the button. The file name typically looks like: VMware-vSAN-Witness-<version>.ova (e.g., VMware-vSAN-Witness-8.0.0-xxxx.ova ).
In vSphere Client → Right-click a datacenter/cluster → Deploy OVF Template → Select the downloaded .ova file.
Check the box that says "I accept the terms of the license agreement" and click the Download Now button. The file size is relatively small—approximately 700 MB to 1.2 GB.