This is a stand-alone program, but it is entirely compatible with WinGX, and reads the WINGX.INI file to determine the current structure directory, and the current version will load name.INS by default. It comes with its own extensive hard-copy and HTML documentation, but the GUI is mostly self-explanatory.
To use ORTEP3 seamlessly in the WinGX system, install the program as suggested in the README file, and ensure that the fullpath of the executable is given under FILES[SYSTEM[Setup].