Optional video tutorial for installing SuperBLT, BeardLib, and mod_overrides mods: https://youtu.be/rin_sjSJIkg

After downloading the mod, use a program such as 7zip or WinRAR to extract the main folder of the mod.
Move the main folder of the mod to assets/mod_overrides. The assets folder is supposed to be in your game's installation folder (don't know where that is? click here). Create the folder if necessary

How to install:
Steam\steamapps\common\PAYDAY 2\assets\mod_overrides