In before the "How do I install it?"
Unzip the file (if it's a .rar file you'll need either winrar or another program to do so, google for them), you'll get a folder with the mods name. Put that folder inside the "Module" folder in your "Mount&Blade" folder, then simply start the game and pick the mod from the drop down menu at the top of the launcher (note, "Native" is the name for standard mount and blade).