Flashing the BIOS is quite easy, it's the consequences if it all goes wrong that's a bit scary. It tends to be about downloading the new data, most likely as an executable, and running it.
Ah yes, just occurred to me that last time I upgraded I downloaded the file, put it on a flash drive; then when in BIOS there was an option to tell it where to find the BIOS version you wanted to load.
What pc model do you have and what are the symptoms? Flashing the bios seems an extreme method of trying to solve a non-boot problem. I've never had to do that to resolve such issues.