Return to Lordaeron

You pick this up from Calia next to the table in Oribos that Tal'Inara is standing next to

Edit: Alliance, you are looking for Genn Greymane in that room. (Thank you Niralina)

Unlocking the Dark Ranger customizations are super simple. All you have to do is complete the achievement Return to Lordaeron. To complete the achievement, all you have to do is complete a questchain. It starts at [npc=173386](horde) // Genn Greymane(Alliance) In Oribos, in the enclave area, where you change covenants. Once picked up you’ll be sent on a 15 minute questchain, where you’ll return to Lordaeron. Upon completion you’ll already have unlocked the new customizations for blood elves, Night Elves & Void Elves. Once you’ve completed the achievement, you can obtain the transmog, however it is limited to hunter only. So if you have a hunter character, you want to do the questchain on your hunter as you will not unlock the transmog if you did it on say for an example your warrior. Once you have tho, you can go the legion class hall and talk to [npc=103693] to purchase the transmog ensemble for 1000g.

Video Guide: https://youtu.be/GxJX2hHlAlU

If you are a hunter, after you have done the Lordaeron quests, go back to the Legion Class Hall, and talk to Outfitter Reynolds (Worgen) and see what new goodies he is selling!