If you want to change Thor from a forgetful chap who can’t even remember why he is in Fortnite into the legitimate God of Thunder, then you will need to finish his awakening challenges. You get Thor at level one of the Battle Pass, and you will get access to his awakening challenges at Level 15.
Keep in mind, for this challenge to work, you will need to be wearing the Thor skin, but any emote will do. You are looking for Mount F8, a pretty regular spot to complete strange challenges in Fortnite over the years. You can find the exact place you need to go marked on the map below.
All you need to do is head to that location, then bust out your emote option. Thor will take on his true form, all glowing blue energy and general godliness. From there, you can finish out the rest of the match however you see fit or work on any other challenges that you have available.
Each of the Battle Pass skins will have similar challenges this season. You unlock them at one level, then a few levels later, you get access to the awakening challenges to open up some skin options. Most of these are tied to a special emote that will change the skin in some way.