Pull the kick panel on either side there will be several white molex connectors, the speaker wires r twisted and the colors r listed above in the attachment. Cut rhe speaker wire according to the color noted, make sure u leave enough room to attach new wires, ie don’t cut the wires too close to the connector or too high on the harness. The output from the radio comes down from the top of harness and the signal to the speaker goes into the molex. Cut that pair in the middle so u have room to splice. The speaker wires r bigger than some of the other wires in the harness and are twisted. U can be verify u have the right wires by ohming the wires with a multimeter, the factory speakers r 4 ohm, u will get that ohm load at the molex not at the other end of the cut wire, since it goes to the head unit.
As far as adding a sub with the non Blows, I mean Bose system, u will have to tap into a door speaker to get signal. Use 2 speakers to tap into, left and right, not front and rear. That’s why LOCs have 4 input wires, for 2 speakers, more signal for the amp low level input (RCAs). Hope this helps.