This application note explains how to boot Emcraft i.MX 6SoloX SOM Satrter Kit from SD Card:

• On the host, prepare SD card with the u-boot.imx image (replace sdX below with the actual device node of your SD card):

~ # dd if=u-boot.imx of=/dev/sdX bs=1k seek=1
...
~ #

• Set S4 DIP switches 1-8 on the baseboard to combination On On On Off On On Off On (Internal Boot, SD).
• Insert the SD card to the board. Power on the board and check on the serial console that the board boots.