Through the Arduino IDE, while you're hooked up to the arduino via USB you can click the top right icon that looks like a magnifying glass, but it's the serial monitor.
Make sure the output is setup
Both NL and CR | 115200 Baud
If you get to :
System Ready..
Waiting for turbo to come online..
But the turbo never comes online, there's a canbus problem, either connected backwards, actuator not powered up, etc
Otherwise if the turbo does come online, you can type output, to get it to spam the screen with a bunch of goodies, and you can test the pin modes by grounding the appropriate brake/perf mode pins and the output should change, to show you the modes indeed changed.