Go to motherboard manufacturer's website.
Download latest bios for your motherboard.
Extract/unzip file.
Put extracted files on USB drive.
Boot PC and enter bios.
Plug in USB drive with bios file.
Go to bios update in your bios settings and follow instructions.
Go to motherboard manufacturer's website.
Download latest bios for your motherboard.
Extract/unzip file.
Put extracted files on USB drive.
Boot PC and enter bios.
Plug in USB drive with bios file.
Go to bios update in your bios settings and follow instructions.
To add to bmockeg advice
Some manufacturers have their own update utility app, which may be easier to use when updating bios, drivers, optional apps.
Good luck