amplifier issues

I'm in over my head with my install and despite countless internet searches I haven't been able to find the answers I need. I'm also new at this so my apologies if this is a dumb or obvious inquiry. Thank you in advance to any and all that take the time to read this post and respond to it. I...

This is my very first time installing a stereo and dont know much about electrical.so I recently upgraded my stereo system, changing the head unit, and adding an amplifier and subwoofer.the previous owner had an out of factory stereo already installed, so what I did was switch the old HU with a...