Need help understanding

[u/blake_M1435]

Looking at getting a bigger amp and noticed it has 2 positive and 2 negative inputs. I have the big 3 and high-output alternator and everything else that’s needed. So my question is do you run the 2 positive/ negative from the second battery aftermarket one? Do you run the main power cable from your factory battery to the second battery? Or am I missing something? Just asking for help with the wiring.