You'll need either a Pack File Manager
or a DB Editor to create and edit modded files. If you're new to modding, I recommend reading the tutorials on this forum about creating mods. Experienced modders recommend that we copy database files and edit those copies to make mods - they recommend that we never edit the game's original files themselves. It's worth knowing that modding can cause crashes, expected side effects and save game corruption. I suggest modding when you are not tired and have plenty of time. I also recommend working slowly, making a few changes and testing their effects in the game rather than making a lot of changes all at once, which can lead to disappointment if one tiny typing error causes the game to crash when you try to start it.
Mods only have effect in the game when they are in the game's data folder: C:/ProgramFiles(x86)/Steam/steamapps/common/empire total war/data folder (that's the path on this Windows 7 PC; different computers may use different paths).
You also need to activate the mod in one of three ways:-
1. With a script file (called user.empire_script.txt, 'save as' in Notepad using Unicode) in your C:/Users/[your username]/AppData/Roaming/The Creative Assembly/Empire/scripts folder. I made an example of a script file, which I'm using to play Imperial Splendour, here. If you use this method, the names of the mods must appear precisely in the script file. If there is a typing error or if the script file lists a mod which is not in your Empire/data folder, then the game will crash.
2. When you have the modded pack file open in Pack File Manager, changing the pack file's type to 'movie' - if you do this, it works automatically when it is in your Empire/data folder, without needing to be activated using a script file or mod manager
3. With a mod manager (there is one for Empire: Total War; I was not able to get it to work, which may just mean that something went wrong when I downloaded it)
When testing mods, if you are unlucky enough to experience saved game corruption (when loading a saved game crashes the game) here is a way which I have found to make the game playable again without needing to completely re-install ETW:
- Find your scripts file. On my Windows 7 PC, this is in: C:/Users/[my user name]/AppData/Roaming/The Creative Assembly/Empire/scripts
- Make a copy of the preferences_empire_script.txt file
and put that copy somewhere else in case you ever want to put it back (I never have, but it seems wise in principle to copy a file you are about to delete)
- Delete the preferences_empire_script.txt file
- Start the game normally; you don't need to replace the preferences_empire_script.txt file beforehand, because the game should automatically detect that you don't have a preferences file and should create a new one for you.