General Diagram for the 2.5 amp Driver. If you intend on using this driver as a standalone unit, not connected to the 3D Printer Main Board, you can use this diagram to connect the various headers and for the microstepping dip switch settings.

The LED and fault conditions: The driver's LED serves to indicate a fault condition. The driver chip has built in protection for overheating and over current. If the LED is on, most likely, the driver will stop until the condition is resolved. If you see the LED on, adjust the vref trimmer. First, connect a multimeter to the pads just next to the trimmer potentiometer and adjust until the voltage is lowered a bit. Alternatively, even though the PCB contains a vast amount of thermal vias and a relatively large ground plane connected to the belly of the driver, there still may be a need to cool the driver chip using a small heat sink. Do this only if you are not satisfied with the performance of the motor at the torque require.