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 for PAYDAY2 folder). Create the folder if necessary
Drop into mod_overrides and then in-game go to options > sounds > custom heist track playlist and then scroll all the way down and check the box
now it should appear when changing tracks, enjoy! <3