DVD LCD in car is said to be 'GPS ready'. It has a GPS option in the menu. What hardware or software do I need to make to work? I've been googling for what 'GPS ready' really means but still clueless on what I really need to make it work.

I don't know the brand because it comes from an 'all-in' car package and I can't find it in the manual either.

Appreciate the help guys!

Thank you!