Bring 4 Heart of Fire, 4 Globe of Water, 4 Core of Earth, and 4 Breath of Wind to Brumn Winterhoof in the Arathi Mountains. Completing this quest will give you access to the Elemental Leatherworking arts. The completion of this quest will prevent you from learning Dragonscale Leatherworking and Tribal Leatherworking; be sure this is the path you wish to follow before doing so.
Elemental leatherworking is what I know, and if you're willing to open your mind to the greater powers of substance, I will share with you all there is to learn.
Know this, [class]: by choosing this path you agree never to learn dragonscale or tribal leatherworking; there is only room for practice of one of the three arts. Furthermore, I'll need adequate proof that you are in tune with the elements of nature; to that end, bring me the purest essences of fire, water, earth, and wind.