Make sure to first have SuperBLT, and BeardLib installed. Click the links in the dependency list.
Optional video tutorial for installing SuperBLT, BeardLib, and mod_overrides mods: https://youtu.be/rin_sjSJIkg
mods
Add a mod_overrides folder under the assets folder (…/steamapps/common/PAYDAY 2/assets/mod_overrides) and slap the folder in