There is no option to upgrade your PS3 copy to a PS4 copy any more.

There was a campaign that lasted from 2014 to April 1st, 2015 to upgrade your copy, but sadly it's ended (the original link is here: http://na.finalfantasyxiv.com/pr/ps4/ps3_users/).

You'll have to purchase a copy of the PS4 version in order to play on PS4. When you purchase your PS4 copy, all you have to do is simply register your PS4 copy's code to your account, and you're good to go!

You CAN transfer your save data (HUD layout, macros, etc.) from your PS3 version to a PS4 version at the PS4 launcher (link detailing how here: http://na.finalfantasyxiv.com/lodest...e/ps4/upgrade/).