Hello,
I have returned back to WoW with Shadowlands and have not played since MoP. I really want to unlock the Kul-Tiran, after I’ve already locked the Void Elves since returning but have no idea how to even begin unlocking the Kul-Tiran and where to find the first quest, any help would be greatly appreciated 
Thanks
For Kul Tirans you need to have completed several quest chains in Kul Tiras for the Alliance. For example, you need to finish the War Campaign, both the 8.0 and 8.1 parts of the Campaign, you also need to complete the “A Nation United” achievement.
So hopefully that can steer you in the right direction now, as always you can ask other players in-game or make use of other fan resources online to check how to do certain activities in the game.
You should probably also use the WoW forums and not the “Classic Games Tech” forum for this kind of thing.
You’re out of luck if you only want to keep it casual, blizzard wants you to spend all your free time playing their game, so they lock new stuff like this behind timegates. It’s kinda like a carrot with a stick.
I had an issue where I was over level 50 by the time I reached the point where I had to clear Siege of Boralus dungeon for the achieve that is needed. At that point you cannot use the dungeon finder to get a group for any BFA content, so I had to wait for days for a group so I could complete that one step. Kinda sucks tbh.