How can i change texture of a game made with unity

I am interseted in make a granny horror game texture but i dont know how it is done i want to learn how is i really done i have tried many softwares like

Unity assest explorer
Unity bundle extractor
Unity ex
Unity dex

I have spent 9 months on this issue but didnt find correct way
I want this particular information for android app

Good day.

Unity is not for creating the textures. You need some other program, like photshop (or even paint if you want). And just need to drop the image file in the assets folder to use it inside unity.