This video shows different ways of installing the Simplygon plugin in Unreal Engine 5. It is also applicable for Unreal Engine 4.
Alternative 2 command line:
.\InstallSimplygonZip.ps1 -ZipPath "C:\[PATH_TO_SDK]\SimplygonSDK_10.0.4600.0.zip"
More installation instructions:
documentation.simplygon.com/SimplygonSDK_10.0.4600.0/ue5/installation/installation.html
Download Simplygon:
simplygon.com/Downloads