Once you hit level 83, the Hero’s Call Board will send you to Uldum. There’s just one little catch to the quest as it’s given.
The quest sends you to a Adarrah’s caravan in Tannaris. That quest starts the Uldum questline. The quest reads “You can reach Adarrah’s caravan from the Eastern Earthshrine….” There is NO portal to send you to to Uldum the first time, you are going to have to get there on your own.
There are different ideas on the internet as to the best way to travel. With “commercial” flights tending to take such scenic routes, I’d suggest going to Booty Bay from Stormwind, taking the boat to Ratchet, then flying to Tannaris
Once you are there, the first few quests should give you a portal for later returns to the area.