This unlocks during the course of the main story, and as far as I know it can't be missed. It unlocks when completing the in-game quest "Karick's Helm Problem" -- this happens about 45 minutes- 1.5 hrs into the game.
After unlocking
you will need to get a helmet unstuck from an NPCs head. To do so, you will need soap.
There is a wiki page for this quest which you may refer to also:
https://nehrim.fandom.com/wiki/Karick%27s_Helm_ProblemYou will need to use a spell or a bow/arrows to aggravate the mages who lurk outside the locked gate.
You can buy a bow and arrow from the nearby merchant NPC on the hill, or you can use one of the magical target spell scrolls that you picked up earlier.
After aggravating the mages, little yellow objects should be on the ground everywhere inside the gate. These are the soaps. You just need one, but you can use the others as ingredients later in the game.