Modify clothes decals

hello, i’m curently try to modify clothes decals but but with no success.

i only find this files like “mp_elite_tshirt_002” or “decl_diff_002_a_uni.ytd” but seem to not working. if you have any sugestion you’r welcome.

ps: i tried that too, but same no result ([Release] + [Tutorial] Add new tattoos and overlays (Example Included))