By the Twelve, this is a pain...had the same trouble with windows, but there is a link for that! I just Googled it and it seems that you must get the link from the Square Enix Store. I don know the policy on posting links here but all I did was search "FFXIV setup for mac". Got a hit on the SE Store, on that page there is a link for the client download under the "Registration Instructions" tab. Maybe try that? Hope it helps xD