Installation:
-Locate Dying Light install folder. 
-In the Dying Light install folder open the DW folder, backup Data3.pak and then replace it with this new one. 

Uninstallation:
-Delete modified Data3.pak, restore backup

Notes: 
-Other mods using Data3.pak will be overridden and will have to be opened and merged. 
-When updated, Dying Light usually wipes the Data3.pak file. Be sure to back up your mods before updating!