This file contains RTW files, at the Patch 1.2 level.
Use overwrite, to replace any existing files.
Extract this to the RTW install directory, e.g.,
C:\Games\Rome Total War\
This file does NOT contain any other modded elements, like graphics or fancy descriptions. You can add these if you want. Backups of each original and the associated modded file are provided, in addition to the 2 modded files.
Note: In Patch 1.2, technically you do not need to include the campaign_descriptions.txt, but it is included for completeness and continuity with later APF modding.