The stock radio does not have an easily-accessible video input. The closest it has is the backup camera input, and that is a proprietary, tiny four-prong plug. You would have to hack the connector AND find out where the backup signal is on the wiring harness.
Your best bet is to get a third-party radio. The "S" model makes it easy. While the radio is just slightly larger than a standard double-DIN radio, there are adapters available.
I have a Sony XAV-AX100 radio in my 2015 "S". It has Apple CarPlay and Android Auto support, and will play videos on the display from USB devices. (Technically, this only works if you have the parking brake set, but it's easy to figure out the no-cost bypass.) It's important to know that CarPlay does NOT mirror your iPhone. It has its own interface and only a certain subset of apps will run (mostly radio apps).
2012 Mitsubishi i-MiEV ES (lease ended) • 2015 Nissan LEAF S • Tesla Model 3 reserved
Mods: Matte black Juke wheels, LED headlights and accessory lights, horn, CarPlay receiver, subwoofer and amp