If you intend to use it as a “Media” drive on the PS4 for playing Movies, Video, Music, Photo’s etc … it needs to be formatted either FAT32 or exFAT. (recommend exFAT since it supports file sizes over 4GB)
If you intend to use it as “Extended Storage” for PS4 Game and App Installations then you need to format it on the PS4 Console.
From your PS4 ™, go to [Settings] > [Devices] > [USB Storage Devices]. Select the [USB storage device] and click [ Format as Extended Storage ].
Note: Once the drive is formatted as “Extended Storage” it can only be used on the PS4 Console for Game/App installations and will not be compatible with your PC. (you can however, re-format back to use with PC under Disk Management … this will erase everything on the hard drive)
Lastly, if you wish to use an External Hard drive on the PS4 for Media Playback and Extended Storage … then you will need 2 External Hard drives to accomplish it.