As far as I'm aware, the NAV setup you have, is Japan only so may not work if your in the US?
The wire coming out of the nav screen would attach to an OEM cable [similar to the cd cable] that runs from the centre console to the NAV unit in the trunk [again similar in the way the oem cd is installed]
My car is JDM and I have the nav cables pre-installed, not sure if its the same for US cars?