Nevermind what I just said, I misunderstood.
First you need to look up the .dds, find the folder path you need to create, and make that path in the data folder
Second, place you edited .dds in the new folder path.
Third, edit fallout.ini from 'bInvalidateOlderFiles=0' to 'bInvalidateOlderFiles=1'.
Last, also in fallout.ini, type in the folder path and name of the new .dds.
Ex: Data/textures/guns/chinesepistol.dds
I FEEL LIKE SUCH A FAGGOT.