I am not sure how to do this? Does anyone know? Preorder content.

According to the devs over on Steam forums, you have to reach "Act2" and find the character that will allow you to do that.

I'm unsure what they mean by "Act 2" as I've yet to reach that part.

Probably wondering around aimlessly for days on end until you think you find something that could be it.

Once you have the choice of three locations to do in any order you choose (Being vague to avoid spoilers) you can find an npc that will allow you to change your appearance located in the underground area, if you want to go there first.

Okay, here's how to change outfits - potential Spoilers:
- You need to get the NPC Asiri from the city of Haven in Kaanul. You need to get the advanced sliding ability from Iron Kingdom first. Once you get Asiri, go left in the Inner Realm towards Nuna's area and Asiri is next to her. Finally, the outfits don't appear to have any special names, they're just Palatte 5, 6, and 7. Screens attached with what each set looks like.

I admit I expected more from the skins. I know, I know, animations and all of that. But I don't like the colors so much. Been using the Cyberpunk one for a while now, though...