Visit your motherboard webpage by searching google for the brand and model of your motherboard. Once there, go to the “Support” tab
Look for BIOS updates, then download the most recent version.
Insert a spare USB thumb drive, it must be formatted as FAT32.
Extract the BIOS you downloaded in step 2 to USB thumb drive.
Reboot the computer then press the Del key repeatedly until the BIOS menu appears.
Navigate to the BIOS update section. That is named differently depending on what company manufactured your motherboard: Asus: EZ Flash Gigabyte: Q-Flash MSi: M-Flash
Navigate to the BIOS update file you extracted to the USB thumb drive in step 4 then press enter.
The BIOS flash begins. It can take up to 10 minutes. Do not interrupt the process in any way, the system will automatically reboot itself when it completes or show a reboot prompt.