itch.io

You need a Torch, it can made in workshop but needs plank + cloth

Or you can use glowing amulet that made by Priestess/Witch by gathering some glowshroom and bring it to one of them

You need 5 glowshrooms and then you can go to the day witch or Othra. You can find glowshrooms at Northcrest cave or at the purification lake. 

(Also in the main menu you can find a guide, it isn't updated regularly, but yeah. This one is answered in there. I also think you can already get a torch somewhere,)

Also don't forget equipping the item