Is there a document or web page that describes how to use GPIO on an Arduino board, and in particular, the Giga R1?
This link might be a good start. Here is another.
These tutorials address Arduino boards that use a different processor than the Giga R1. Still, the beauty of the Arduino software infrastructure is that once you select the correct board in the IDE, many examples are portable from one board type to another.
Try a web search for other examples, and you will see that there are many.
Thanks!