From Webopedia:
On PCs, the BIOS contains all the code required to control the keyboard, display screen, disk drives, serial communications, and a number of miscellaneous functions.
The BIOS is typically placed in a ROM chip that comes with the computer (it is often called a ROM BIOS). This ensures that the BIOS will always be available and will not be damaged by disk failures. It also makes it possible for a computer to boot itself.
Check first to see if you even need to flash (update) the bios.
Usually when you first power up computer the initial text on the computer screen will tell
you which version of bios you have.
Sometimes it is printed on the motherboard.
Then you will probably have to go to the motherboard manufacturer site and download the latest bios. There should be instructions there on how to check and "flash the bios".
But for a noob I'd suggest if it ain't broke don't fix it.
You can do damage if not done properly. (although it is usually easy if you follow the manufacturer instructions.)
You may or may not be able to use a USB flash drive to do it.
What motherboard do you have?