Front door speaker wiring help

[melrap]

Hi everyone, forgive me if im doing this wrong but i am totally new to forums and how they work.  I am replacing my stock speakers with components that i have.  Not using the mid or the crossover.  i am completely confused on how to wire the woofer in.  which speaker wire do i use? i see it in two spots.  What i have done:
Tapped into speaker wire from the two wires that went to stock speaker, no sound
Tapped into speaker wire at crossover harness, not connected to the crossover
Tapped into speaker wire at crossover harness, connected.  I either get low output or nothing.  I have seen numerous threads and videos of how to's but it isnt clear to me how to wire the woofer in.  Most how to's use 3 way systems which i am not using.  if anyone can explain this to me i would greatly appreciate it! im stumped

[Shamm]

Get a rca adapter and do it through the headunit much easier

[melrap]

my head unit already has the amp connected via rca's, thank for the reply

[Xaire]

Are you using an amplifier? If so, which model? If you used it, then you would have absolutely no problems with the connection, since everything is intuitive there. I have an additional amplifier installed in the trunk, as well as two subwoofers, because of which there is almost no space in the trunk. As a result, when I purchased new doors for my house from doordesignlab.com, I had to order delivery instead of picking up the doors myself. Of course, it seems to me that high-quality music is much better than an empty space, which is extremely rare, but the situation was really not very pleasant ...