Hi, 

you can either go this way (manually) or use the more simple way:

1. The very first boot of Example Image V1.2.1 from SD card will show a orange STAT LED for 20 seconds
2. In this state press and hold the USER Button for 5 seconds (STAT LED blinks red in this 5 seconds)
3. Now the STAT LED starts to blink green and the Example Image gets written to the eMMc
4. After about 10 minutes the IOT2050 automatically reboots (will end up in SD card again, when SD is set a first boot device) 
5. Remove the SD card and boot again --> IOT2050 boots from eMMc with Example Image V1.2.1

Best regards!