If you are referring to USAD system files, save them to your pc, in the folder labeled "USAD_Systems". That will be a subfolder of the "BC396T USAD Database" off of 'My Documents', unless you specified a different install location. Some of the files listed in the Yahoo group have a "*.zip" extension, so you'll need Winzip, PKZip, or another compatible utility to uncompress them.
What I prefer to do is to, instead, save the file(s) to a different folder, then rename it before moving to the "USAD_Systems" folder. That way you don't accidently overwrite your own file with the same name.