Download this INSTEAD of SLUMod1.0, as 1.1 is a much smaller file that will download much faster, with all the required updates.
A new (fairly minor) update more aimed at housekeeping and ease of download rather than anything else, but I really would recommend downloading it for for future updates.
Description of what I have changed can be found here: Moddb.com
2. Unzip file into mod folder
3. Go to steam and right click on Medieval Total War 2
5. Select Properties
6. Click [set launch options]
7. Paste this [--features.mod=mods/SLUMod1.1] in the box and click ok.
8. Launch the game
If the UI is glitchy with this mod on your computer, copy the UI folder from vanilla and insert it into the mod, not replacing the documents/items already there.