After opening the app, follow these instructions.
1. Connect to your Chromecast using bluetooth.
2. Once connected begin the process to connect to Wi-Fi.
3. On the bottom right of the page which asks you to select a Wi-Fi network, the MAC address is displayed.
4. Do NOT select a network at this point.
5. Once you've located the hardware address for your device, you can register it following the instructions for Connecting your streaming media player.
6. After registering the device on the network, resume the setup via the app.