The wiring diagram is pretty self-explanatory. Connect motor driver and opto-fork power inputs to Raspberry Pi 5V. (This assumes that your motor uses less than 500mW of power, and can run on 5V, like the listed motor. Also assumes that your opto-fork is 5V.) Opto-fork's LED should have the 150 ohm resistor in line, to limit current.

Opto-fork's open-collector output needs the 10k ohm resistor pulling the signal toward 3.3V. But don't forget to connect the output to the GPIO pin too - making sure to connect the OTHER end of the resistor, so you don't short-circuit 3.3V to GND when the opto-fork output goes low.

I connected opto-fork output to pin 17, and motor control 1-4 to pins like IN1->GPIO27, 2->22, 3->23, 4->24. Note that the pin order in software needs to match the motor driver's input numbering, or the motor will not move right.

For building the software and configuring, see the file README.txt, in this project's files.