burn uboot/kernel/roofts to nand flash by uuu

[aoboyan]

I want to ask you a question how to burn uboot/kernel/roofts to nand flash by uuu. When use this command that "uuu -d -v uboot.imx", this HID device is disappeared in vmware workstation of ubuntu16.04. I try to use  imx_v2018.03_4.14.78_1.0.0_ga but xshell show that "## Checking Image at 83800000 ...
Unknown image format!
Run fastboot ...
Unknown command 'fastboot' - try 'help'
"

Is uboot files needed to add others fastboot items?

Please, could you give me a detail Guider manual 

chip is imx6ul 

[Rita_Wang]

Are you using the NXP i.MX6UL EVK board or board you designed yourself? When you use the uuu to download, have you set the right images? You need to check first.