RECOVER CHROMEBOOK USING U-BOOT --3

I have SAMSUNG CHROMEBOOK Series 3. After removing the WRITE PROTECT from the internal motherboard, I installed LINUX as a dual boot system. Then - I accidentally repartitioned the drive so that both the original copy of CHROMEOS and my copy of LINUX are both gone. The CHROMEBOOK will start up and logs into the U-BOOT system, which is Chrome's version of GRUB. I have a USB stick with a copy of the rescue system on it, but I cannot figure out how to boot up off the USB stick, or to repartition the internal drive using U-BOOT, or to copy the partitions from the USB Stick to the internal drive. I need someone who knows how to use U-Boot to help rescue this system. You will also be aware that U-Boot on a CHROMEBOOK is non standard and does not have all the commands (such as NAND) available.