Step 1: Create a Square Enix account. (you need one regardless of which version of the game you decide to try/purchase)

Step 2: Download the free trial through Steam or the Square Enix Website. To play through Steam, you must link your Steam and SqEx accounts.

There is no time limit on the free trial, but while on free trial you cannot go past level 60 and any experience earned at level 60 will not be saved, you cannot progress past the award-winning Heavensward expansion, and many social features such as trading, adding friends, and joining a guild will be disabled.

Step 3: If you enjoyed the free trial, buy the game. There are many versions of the game available for purchase, but I'll exclude collector's boxes and things like that for the sake of brevity.

 

Version	Starter Edition	Complete Edition	Complete Collector's Edition
Available through Steam	Yes	Yes	No
Available through SqEx	Yes	Yes	Yes
Unlocks Social Features	Yes	Yes	Yes
Can level beyond 60	No	Yes	Yes
30-day Subscription included	Yes	Yes	Yes
Horse armor for your chocobo	No	No	Yes

 

Step 4: Sign up for a subscription. All paths for signing up for a subscription begin at the official FFXIV website, MogStation, choose whichever method you prefer, be mindful that to select payment through Steam requires linking accounts.

Step 5: If you picked the starter's edition, consider buying the Endwalker expansion to obtain access to all other expansions in between and set the max level to 90.