The Burning Crusade welcomes you to Outland. A new place to explored with lush environments, exquisite biomes, and people to gank.
To get to Outland differs depending on if you are Alliance or Horde, but both have to go through the Dark Portal to reach the land of the expansion. The Dark Portal allows you to travel between the two realms, Azeroth and Outland, freely.
How to get to Outland as Alliance?
First, off wherever you are, head to Stormwind, and then take flight to Nethergarde Keep, in the Blasted Lands. From the Keep, travel in a south-southwest direct where you will find yourself at the Dark Portal area. The portal is hard to miss as it's gigantic. Head through the green portal to appear in Outland.
How to get to Outland as Horde?
Travel to Ogrimmar, and head towards the Zeppelin located to the west. Take the Zeppelin to Grom'gol, and then take flight to Stonard. Now you need to travel south on foot or on mount to enter the Blasted Lands. Upon entering, follow the path south until you see the massive portal, and like the Alliance, head on through the green glow to arrive in Outland.