How do I mod DLCs?



Could anyone explain to me how I can mod content from the DLCs? If I use the normal folder path, the policies show up twice in game (and since there are 4 files for the vanilla game and the DLC that all use the same name they conflict), if I use the folder path that leads to the DLC folder inside my mod folder the changes won’t show up at all. I have the game on Steam by the way.