your head unit is just like every other aftermarket unit. there are a set of rca cables, they are like speaker wires but in a nicer form(the red and white). so for adding a sub on your unit you use the gray set or rca cbles, they are the ones for the rear audio and the black are for the front.
to wire a sub you need a wire kit, or you can buy everything separate. the basics to the kit are: a power wire form the battery with an inline fuse holder, ground cable, rca cables, remote turn on lead, and speaker wire.
the rcas and the turn on lead get pluged into the amp from the headunit, the power goes from your battery to the amp, gorund goes to a ground location, and speaker wire to go from the amp to the sub(s)
so for a rear amp use the grey rca's and the turn on lead is the blue wire or the blue with a stripe wire. on your unit it is a blue wire marked as the power antenna