its by the passenger side kick panel the 1 with the light in down by your foot you need to remove this then what you need to do is buy the an after market loom for a ford

all the speaker wires go into the amp then from the amp there is a ford cable upto your oem stereo

what you need to do is remove both stereos and remove the ford wiring between them you will then be left with the oem power connector

and the cable to the amp you then buy a harness to convert these to your stereo what you might find is thet you will need to extend the 8 speaker wire connector down to the footwell