Step #162 in the Expanded Vanilla list
Do not use the included esp! This is listed as partially working because a patch is required for this to work with OpenMW, see Welcome to the Arena v6.7 patched for OpenMW for the working plugin.
OpenMW 0.46.0 or newer required. Set
apply lighting to environment maps = true in the
[Shaders] section of your
settings.cfg file to fix shiny meshes, see this page about "shiny meshes", and this page about the settings file for more information.