Click to enlarge.

The lipoly backpack sits atop the audio FX board with the provided headers. Other connections as follows:

• trigger pin 2 -> GND
• potentiometer first leg -> GND
• potentiometer second leg -> audio board R
• potentiometer third leg -> amp A+
• amp A- -> GND
• amp Vin -> 5V
• amp GND -> GND
• switch leads to lipoly backpack (after cutting connecting trace)
• switch LED + -> 220 ohm resistor -> 5V
• switch LED - -> GND
• amp outputs to speaker