The serial number can be found either:
1. On the bottom of all Elite ECUs and on the USB port side of the Platinum ECUs. 2. On your purchase invoice/receipt, or 3. Connect to the ECU via your old crusty laptop, then go to Tools > Firmware Version, and the Serial number is shown there.
ECUs must have been purchased in either December 2017 or January 2018 to be eligible for entry.