First of course you gotta download the mod so here Is a link to get started https://www.moddb.com/mods/american-civil-war-the-blue-and-the-grey/

Once Its finished go Into your file explorer and go to downloads and just open It. Also I use Winrar to open It so If you need It here Is the link https://www.win-rar.com/start.html?&L=0

So once you locate It of course click on It and you will see whats In the folder

Once you click on whats Inside you will get directed to a Installer and yeah

Just press next and agree to the terms then you will get to the part where you direct your total war so make sure you now where It Is a good tip Is to right click your Empire Total war and press browse local files and at the top It tells you but once you figured out where It is direct It and click Install.

After Its done you get a Installer on your desktop click on It. It will tell you to choose CSA or Union It also tells you to enable zone of recruitment so do that and then undo It but you choose a side and It will start.

This mod was not made by ME so yeah and also there Is a bug thats happens with It saying no vannila files and It will give you a error message If you launch the launcher the fix Is to ignore that error and when It gives you the error message just go to Steam and launch Empire Total war.