@HinataGrape-6694, to update the Azure RTOS portion on an IoT device is similar today to update the entire firmware which Azure RTOS now has already supports by using the Device Update for IoT Hub service: https://learn.microsoft.com/en-us/azure/iot-hub-device-update/
And you can try with some key boards we already have samples for: https://github.com/azure-rtos/samples/tree/PublicPreview/ADU
And like @Scott Azure RTOS mentioned, we are yet to include the secure boot as part of the sample to ensure the security on the device end. Please let us know further questions you have on this.