1. Find where your PAYDAY 3 copy is installed. The location of this folder will vary depending on your installation preferences & storefront.

• Steam
• Epic
• GamePass

2. Installation:

• Mercury Mod Manager
  If you have Mercury Mod Manager installed extract the contents into .../PAYDAY3/Binaries/Win64/Mods or .../PAYDAY3/Binaries/WinGDK/Mods

• Manual
  If you don't use Mercury Mod Manager or prefer to just use the default UE4 pak mounting extract the contents and move the mod .pak file into .../PAYDAY3/Content/Paks/~mods. Create the folder if necessary.

Just paste it in your "~mods" folder