Connections: Connect the motor driver on the breadboard and then follow this wiring diagram:
If in doubt, refer to the A4988 wiring diagram (for example this one) and the technical specifications for the engine (available here). Be careful to correctly connect the wires from the DC socket to the breadboard, respecting the polarity of the power supply. Also, take care to the polarity of the capacitor. Finally, we must connect the output "Step" to pin n°2 and "Dir" output to pin n°3 of the Arduino (this connection is compatible with those specified by DragonFrame).
Once this step is complete, the Interior of the case should look like this: