https://blog.eu.playstation.com/2017/03/10/how-to-download-and-store-ps4-games-and-apps-to-an-external-hdd/
You may have to reformat , since 4.5 firmware & for ps4 game use the drive has to be formatted in a special ps4 file format.
This makes it useable only for the ps4 then unless you reformat it again on a PC for general use.