Not really a DIY task, since in all probability the electronics for the cassette player were embedded with the radio.
If you have a complete radio/CD player, then you have to look for:
Power supply connections (a cable that provides 12 volts when the ignition is on)
The incoming aerial (will be a co-ax cable about 5mm diameter, probably connecting into a flying socket)
Identify the speaker connections (with a good bit of luck this and the power supply might be on a common plug-in connector)
If there is no plug-in connector, which I strongly doubt, then you will have to use a chocolate block connector, but you can identify the speakers one at a time by touching the cables onto an AA battery, whereupon you will hear a soft pop.
The picture below is not a Jazz/Honda connector, but just a generic one that is used by some car radio sets
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