Go into your “System Properties” (Control Panel > System > Advanced system settings ) then click on “Environment Variables”.
Locate the PATH variable, either in the “User variables” or the “System variables”. Edit the field and add the path to the MiddleVR bin folder, typically “C:\Program Files (x86)\MiddleVR\bin”.
Warning: The environment variables are loaded at the startup of an application. If you change any environment variable, you have to restart all the applications that depend on this variable. For MiddleVR for example, make sure you restart Unity and MiddleVR config, and possibly any windows file explorer instance that you use to run your applications. The easiest method is to simply restart your computer.