Author : erasmus777
Original Thread : How to Create a Mod

How to Create a Mod
The short version:

How to make a mod:

  1. Download the Pack File Manager for NTW.
  2. Create a new folder called "My Mod Folder"
  3. Open PFM and click File>Open
  4. Navigate to C:\Program Files\Steam\steamapps\common\[napoleon total war?--guessing cuz I don't own the game]\data
  5. Find the .pack that contains the tables you want to edit and open it.
  6. Right-click on the tables you want and select "Extract..." or press Cntrl-X. Extract the table to the folder you created in Step 2.
  7. Repeat #6 as many times as you need.
  8. To create your new mod .pack, click File>New.
  9. When PFM asks you what folder you want things to be relative to, select the folder you created in Step 2.
  10. Right-click in the left window and select "Change pack type>Mod".
  11. Press the "Insert" key or right-click in the left window to add the desired tables to your new .pack.
  12. Save.
  13. Click "Options" above the right window and uncheck "Use first column as row header".
  14. Shift-click the empty cells in the first column to select the blocks of rows that you don't want to edit and press "Delete". If you're not sure, you can do this step later.
  15. Go through and rename all your tables by right-clicking and selecting "Rename". It doesn't matter what you name them, just rename them. Note: Do not rename the folder. E.g., change "units" to "best_mod_ever_units", but do not rename "units_tables". See the screen shot in this post.
  16. Edit your tables.
  17. Save often.

Next... the script file. For now, check out:

NOTE: If your mod is loading fine, but you're not seeing your changes in-game, read husserlTW's note below--
Spoiler Alert, click show to read: 
... I've seen many reports about mod.packs that do not work as "mod" type and you have to make them "movie". Until now I have not any such problem working with factions, units and custom units for my mods. Avoid to make "movie" mod.packs (exceptspecial occasions like _loc files, videos, etc.) because later you might have problem as happened many times in Empire. Movie packs do not need activation through user.script or Mod Manager (if later is updated for Napoleon) and are easy to be forgotten. These remaining "movie" packs can cause conflicts with future mods you are going to use or with vanilla. Conflicts will be responsible for disabling expected elements of a mod or vanilla and sometimes for unexplained CTD's.