You have a couple of options. You can simply use the last binary you had to reprogram the board and open a serial connection, reset the discovery kit and as soon as it reboots the LoRa credentials will print to the terminal.
The other option, if you want to set new credentials, is to enter new values into commissioning.h. If you want to set a new DevEUI instead of using the one generated by the board unique ID function then you also need to set STATIC_DEVICE_EUI to 1 in commissioning.h.
