Just drop the "Black Raincoats" folder to the "mod_override" in your payday 2 root which is localized in "assets" or simply make one.

E.g

C:\Program Files (x86)\Steam\steamapps\common\PAYDAY 2\assets\mod_overrides\Black Raincoats

C:\Program Files\Steam\steamapps\common\PAYDAY 2\assets\mod_overrides\Black Raincoats

Enjoy! -Matthelzor