The process involves removing the A4988 IC from the board (either by severing the connection closest to the chip or using hot air to lift the chip off) and then tapping off of the logical voltage connections on the board (refer to the picture below)
Red is the 5V logic voltage that should never be connected to 12V (DO NOT tie this to 12V rail. This will fry everything on the board.)
Orange is the direction, yellow is the step signal, magenta is the Enable pin, teal is the 12V motor power connection and green is the microstepping configuration (which in this case is just set to 1/16 step mode)
Both Reset and Sleep pins are disabled through the resistor.
Strangely, both NTC and fan connections are present but never utilized.
While you're at it, you might want to tape the buzzer so it's quieter.