IMPORTANT NOTE: Before installing the Witness TMG Program, in order for the Witness TMG Program to be able to read the internal files of The Master Genealogist, one must first install the Microsoft VFPOLEDB facility.
This can be gotten from: http://www.microsoft.com/en-us/download/details.aspx?id=14839
I believe that one may choose either of the relevant installers to download, although I have used VFPOLEDBSetup.msi. After the VFPOLEDB facility has been installed, one may install the Witness TMG Program.
All that is strictly required is that the GEDCOM file have the same numbering conventions of the TMG file and that the TMG file include all individuals that occur in the GEDCOM file. This requirement is most easily satisfied if the TMG project is the project file used to generate the GEDCOM file or a superset of that project file.
The WitnessTMG package is in the form of a zip file, whose only contents is the WitnessTMG.exe program. After downloading, one should extract the WitnessTMG program and store it in a folder of your choice. You can run it from there.