To install the mod: Copy both of the files (*.dat and *.cat) into your X3\mods-folder. If you have not used mods before, it should only contain a 'dummy.txt'-file at this point. This is the correct folder...

Then when you start X3, from the launching application click the "Select Mod Package"-button. The mod you installed should be listed. Select it and click OK. Then start the game and the mod is used.