Please download the flashing utility from the link below:
https://www.supermicro.com/wdl/utility/IPMI%20FW%20flash%20tools/SMT/Dos%201.15.zip
Unzip the file and copy the content into a bootable USB flash drive. Also copy the image file (filename.bin) to the same directory. Boot the system to the bootable USB flash drive. In the DOS prompt, go to the files directory and type:
> dUpdate.exe -f filename.bin