Warrior is one of the two first tanks you can play in Final Fantasy XIV and the funniest for me as the job is the only one to feature fell cleave in the game.
To unlock Warrior players will simply need have either started as a Marauder when they created their character or go to Limsa Lominsa to unlock the quest. Marauder is the first part of Warrior and will only last until lvl 30 where you'll upgrade to Warrior. The quest to become a Marauder is given by the Marauders Guild in Limsa Lominsa (X: 11 Y: 6).
Upgrading from Marauder to Warrior will be done by taking the quest from Wyrnzoen in Limsa Lominsa Upper Decks (X:11 Y: 6), this will start your Warrior quest line.
The Warrior questline features 19 quests. During these 19 quests nine of them will unlock new spells so make sure to do them all if you plan on using the job!
The last quest of the series is a yellow quest so you might miss it if you don’t pay attention.
FFXIV Warrior Quest List
Once you finished the job quests you will also be able to take on your role quests. These quests are shared between all the classes from a same role so you'll only need to finish it with a single job.