A good way to do this is looking at the Table 4 (Page 10) of the Hardware Guide for the Arduino Expansion Board you will see a column called Pin inside the SoC pin modes section. All those GPXX- pins you see there you can check them in the Breakout Board Hardware Guide, Table 2 (Page 9).
For example: IO0 | GP130 | J18 - pin 13
CMata_Intel -- This is close, but not quite there. The problem is that the translated pin is J18-13 which is a string, not an integer. For the Arduino functions like digitalWrite() and stepper.step(), an integer is required so the string doesn't work. I need one more translation here from J18-13 to whatever the actual integer pin is for Arduino. Typically the PWM pins in Arduino are 3, 5, 6, 9, 10 and 11. But I don't see where these numbers translate the Jxx-x to an integer value. Any suggestions?
Using the Breakout Board and the Arduino IDE you can use the integers for those functions, then you will have to check the hardware guides as I mentioned above. For example, if you want to use the pin 7 in the Arduino IDE you will need to check the IO7, this will guide you to use the J19 - pin 6 in the Breakout Board. This is because the Arduino IDE is intended to work with Arduino boards and the Galileo and Edison with the Arduino Expansion Board because have the same pin distribution. You can use the Arduino IDE with the breakout board but you will require an extra work like:
1. Check the right pin you want to use in the breakout board and compare the pin with the Arduino Expansion Board.
2. The pins in the breakout board have a maximum voltage of 1.8V so you will need a voltage converter if you need 5V signals.