The installed Maxwell Render environment can be set in a dialog which is located under Edit -> Preferences -> Maxwell Render Settings… in the menu.
The dialog expects the location of the Maxwell and Mxed executables. When the path changes the plug-in verifies if the given file exists and displays an error message if not.
If the MAXWELL2_ROOT environment variable is set then the plug-in will use it by default and no manual settings are needed.