Inspired by this video ------>  https://www.youtube.com/watch?v=M6Ae8UAXgl0

Extract zip file and place file wherever you'd like.

Open up uMod and boot up Rocket League when the game has loaded up go back to uMod make sure you have global hook on and click on add game and select the RocketLeague application on the 'Main' tab. Then right click on the empty box under 'Title' and select 'Open texture/package and select the file you just downloaded and select the Images and press ''Ok' x 2. Go back into Rocket League and the textures should be loaded.