i have a box around with 2 subs.. and i was wondering where would i hook up this? do i have to tap wires or what?

 

oh and i want it to work with the existing oem sub woofer? is that possible?

 

Although it is probably not powerful enough to drive the aftermarket sub you have properly, you would need to find the speaker leads that go to the stock sub, disconnect them and connect them to your sub, don't be disappointed if it sounds like crap, the amp and x-over point used was designed to drive the stock sub in the box that it came in, not an aftermarket sub.
My guess is you will need to add an amp for the new sub to power it properly. 94

 

Yeah, you definitely want to amp your subs, in which case you'd be better off going to a shop and either getting some advice, or have them do it altogether.

 

buy an amp and a line level adapter. What is the RMS power of your subs?