Hi, welcome. Adafruit have a tutorial for their board [here], which includes wiring diagrams and Arduino code, in the Gadgeteer world the most convenient way to connect to external non-Gadgeteer boards like this is to solder a row of ten breakaway pin headers to the holes in the Extender board, the Adafruit board’s come with some too, then you can stick both in a breadboard and connect up the relevant pins using jumper leads. In this case, connect GND on the Adafruit board to GND on the Extender, VCC on the Adafruit board to 5V on the extender, and the three remaining pins (DO, CS, CLK) to three digital IO pins on the extender, e.g. pins 3,4,5. Lady Ada’s tutorial includes some Arduino code, which you’re going to have to adapt for Gadgeteer - in this code you can see that the interface to the board is essentially SPI, a form of serial communication, so the extender board will go in an S socket on the Spider. There’s some tutorial code on the wiki about SPI [here] which you might be able to make use of in adapting the Adafruit Arduino code into NETMF.