I meant the car wiring, for example one of my cars had never been touched, so i could unplug the OEM headunit and plug the car wiring plug in the Supercheap plug I linked above, which converts to ISO, I was then lucky enough to have bought a head unit that came with ISO plug that would plug directly into it.
It looks like your headunit wiring is just wires at the end, so you would need the second plug i linked from eBay to wire up to the headunit wires that would then plug into the ISO to Nissan adapter into your car. like so: https://upload.wikimedia.org/wikipedia/commons/thumb/3/34/ISO_10487_connector_pinout.svg/220px-ISO_10487_connector_pinout.svg.png
HOWEVER:
If your car already has an aftermarket headunit in it, then it's likely that someone has already cut and wired in the current headunit so you won't have the nissan plug and will have no need for the Supercheap Nissan to ISO adapter.
The actual wiring itself you'll need to just research I guess, off the top of my head REd is 12V Ignition, yellow is battery, black is ground, grey and white are usually the speakers, but exactly which speaker is which will take some testing.
I'd say first step is to remove the headunit that's in your car and see what the wiring situation is behind there. Oh and watch that MCM video, I'm sure that will help.