How to swap capes (not with MESH swaps)?

[General Slushy]

I'm hoping to edit a skin to have a different cape. I've seen mods that do something similar such as giving Batman Beyond a proper cape or fixing the Flashpoint skin by replacing the cape with Earth-2's.
https://www.nexusmods.com/batmanarkhamknight/mods/1169
https://www.nexusmods.com/batmanarkhamknight/mods/645

I'm using UPK Explorer, TFC Installer, and have Photoshop CS6 to edit textures with.

How do I do this?