They are set by an environment Variable. The DS provided standards files are at the location specified by CATDefaultCollectionStandard, and the Company Standard files should be stored at the location specified by CATCollectionStandard. I strongly recommend that you copy the DS ones, and then modify the copies. I also recommend that you do this thru the CATIA Standards Editor, rather than by editing the XML, as it's easy to corrupt the file by getting things in the wrong order.