solid led:your negative wire will go from your switch (wifi, hold, another switch) to your negative wires from the leds.
sound reactive: with an lm386 theres 3 negatives or more if u have mor eleds. 1 from the chip, 1 from the switch and 1 - unlimited -wires from yoru leds. Direct contact. positve and negative wires run to the + and - poles on the speaker. then you add another negative wire to the bunch of negative wires on the speaker and hook that wire to your switch