Earn at least Friendly reputation with the factions of Kul Tiras:
Order of Embers.
This quest starts and ends in Boralus.
"The people of Kul Tiras are diverse and capable. If we can bring them all together under the banner of the Alliance, the Horde has no chance of stopping us."
Here you can buy Uniting Kul Tiras for EU or US Servers.
You'll get guide for completing Uniting Kul Tiras
BfA World Quests unlock (Alliance)