First, you would need to install the NDI tools from NewTek in order to use the NDI feed of the camera.
You would also need to install the OBS NDI plugin for OBS.
The OBS plugin will add a new source type that will be listed as NDI Source. You would want to add the camera as an NDI source, it will not show up as a Video Capture Device.
Thanks Colin. I kinda worked out what to do (as you suggest) after my posting. I think I was following older instructions that asked me to copy files into the plug-in directory. But getting the NDI tools and some packages from Github did the trick. It's all working now. Thanks again.