You will need program OpenBRF
http://www.mbrepository.com/file.php?id=1466Go to Napoleonic wars folder, then to resource folder and open file where should be your uniform located at. For example, I want to change French grenadiers uniform texture. Then I need to go to mm_french_uniforms (im not sure whats the real name of that file). You will need to find what uniform do you want to retexture. Ctrl+F will help here. When you found mesh of that uniform, select it and look at "Texture" (thats written here when you select mesh). For example, there is written " fr_grenadier_a_pied3" . When you find out whats the name of texture, go to Textures file in NW folder, and search for that name. You can then do anything you want with that texture. For texturing you can use program GIMP, which requires to download .dds plugin, or Paint.net. Photoshop is best, but costs money. Remember, everytime you save texture, save it in .dds format!
Hope it helps and good luck