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

1. After downloading the mod, use a program such as 7zip or WinRAR to extract the main folder of the mod.
2. Drop that folder into the mods folder which is supposed to be in the game's installation folder (don't know where that is? click here)

unzip file
navigate to your payday 2 files
assets/mod_override
move all dbd folders (or just the ones you want) into the override folder
load up payday 2
options/sound/custom menu playlist
checkmark all the dbd themes