In content_Browser Manage to Mod folder inside that mod folder create NEW folder where u mod will be.
Any changes u do u need to put all files in to that mod.
So once u in that mod click > Right click> blueprint>all classes>type in BP u wana copy> Select it>Select button>type name and u done.
U need PrimalGameData and TestGame or GameTest cant remember how it is. Link them up together. Then u need to go to each of them and trace down Player UI or something like that. Once you do that, reference the right UI file.