Anyway, just fly back to your faction capital in the Valley of Eternal Blossoms, you'll have a quest taking you to the Dread Wastes there. It will also unlock the flight path to where you need to go.
You can also cross the fallen tree log bridge that crosses the Widening Deep at the south end of Townlong Steppes. It's the place you helped the brew-panda kill the mantid elite.
Bear to the left at the end of the bridge and you'll see a pandaren camp at the base of a big tree. There is a flight point and a breadcrumb quest here that will get you to the starting point for Dread Wastes.