This video show how to install the Creator Ci40 firmware using a FAT formated micro SD card and the preinstalled u-boot.
The commands are simple:
list files on the SD card:
fatls mmc 0
load the file into memory:
fatload mmc 0 address file
All the rest can be found in the Creators documents (how to prepare the NAND, and write data to it) I used a different address here than in the documentation because the image I have is quite big (~74MB)