Basically when the program starts you are presented with a kind of cmd prompt where you can navigate through the directories as you would with ms dos. Youll need to navigate to the directory where the system hives are. eg: C:WINDOWSSYSTEM32CONFIG. In this folder will be the hive files (eg: DEFAULT; SYSTEM; SOFTWARE; SAM) to load one of the hives type load hivefile. This will validate and load the hive. If successfull you will be presented with the editor prompt where you can navigate through the hive and make and read write operations. Note that the hive is loaded into memory so no changes are made to the hive on disk unless you choose the save command.
An important consideration is that if the system drive is formatted to NTFS then the program wont be able to access the drive. You would need to run NTFSPRO v5 with the /S switch pointing to the MSDOS command line interpreter eg: NTSFPRO /Sa:command.com. Once NTFSPRO is loaded you can access the NTFS volumes as you would FAT volumes. So then you can run he_caus.exe.