You cannot simply install a PKG file on a standard, retail PS4 fresh out of the box. The console has security measures to prevent this. To run PKG files, your console must meet specific criteria:
Downloading copyrighted retail games that you do not own is illegal. The homebrew community strongly advocates for using tools like Dumpers to create your own personal fPKG files directly from your physical retail game discs for preservation. If you want to tailor this guide further, let me know: God Of War 3 Ps4 Pkg