Remove the old headunit and the cage surrounding it. Intsall the new cage that came with you new head unit, then goto Halfords, Ebay or any good car audio shop and get a Mazda to standard ISO wiring loom adaptor. Connect this between the loom in the car and the loom on the new head unit. connect the aeriel cable then slide the whole thing into the cage until it clicks into place. Job done.
Steve Graham, January 2006