To install this mod, put the ANIMATEDBATMAN folder in steamapps\common\Batman Arkham Knight\DLC\313100 (or if you don't have the 313100 folder, put it in any other folder in DLC, and if you don't have any folders there, get a DLC, you'll need it). You'll need the Season of Infamy DLC for this skin. If the installation works, in the game, you should have a new showcase in Players, select it as a skin. Done, you can play with this skin in the AR Challenges or story mode.