How to hook up subs to factory?

Hey I need helping installing a system to a factory head unit first off I have a alpine type r dual 4 ohm coils bridged to eight ohms also an amp Sony explode 600 watt amp bridged and a fierce audio line out Put converter. My car is a Toyota avalon 2000 with a jbl system in it do it has a factory amp and sub. Now I know how to wire the amp but everything else I need help withHow to hook up subs to factory?
the sad part is you have to find out how to by pass the old amp and sub woofer and it could possibly be running your speakers to so i think you need to pick a pro installers brain about how you can do this.all information is free there they know they have to explain what the job consists of so they can rob your eyeballs out of your head,just tell him you need some time to think and you will have at least some of the answers,and if you don't get enough Information from one place go to a second and start picking another brain lol.hope this helps you out.How to hook up subs to factory?
Somewhat

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