Go to mogstation in a browser and enter the code for pc version into the account info page, its not that hard to find. Then install ff14 onto a pc and just use the same login info to log into pc version as the ps4 version.
There is one detail and that is you need base game with all expansions. That means the stormblood version which includes base and the previous versions and then shadowbringers.
Do take care not to get it on steam perhaps.