Go to twilight highlands from portal in Stormwind or Orgrimmar Or fly.
The entrance are located up in the air and you therefor need a flying mount to access it. Look where i ping on the map and you will see a ''spire'' there, at the top of the spire you find the entrance. Sorry for the short video but this is all the information you need to find it.
![](https://i.ytimg.com/vi/fpS0-ybfTM0/maxresdefault.jpg)