Preliminary steps
1. Download POLUtilis and launch the program
2. Click "FFXI NPC Renamer" and read the disclaimer

Manually editing mob names
1. Within the "Area" section, search for the zone of the mob you wish to rename
2. Select the mob you wish to rename from the list provided
3. Click "Show Chanes..." to make a list of edits appear
4. Click "Write Pending . . ." and close the application

Using a premade mob rename list
1. Click "Apply Chaneset" and locate the XML file you wish to use
2. Click "Write Pending" and close the application

After you have completed these steps, reboot FFXI and make sure the mob's name appears differently