Good advice to keep your token secret! Here’s how to read you mac address:
byte mac[6];
Network.macAddress(mac);
Serial.print("MAC=");
for( int i=0; i<6; i++) {
Serial.print(mac[i]>>4,HEX);
Serial.print(mac[i]&0x0f,HEX);
if (i != 5) {
Serial.print(":");
}
}