It's unlikely that there is documentation about your BIOS and/or
motherboard with your computer,but if there is read it.
When your computer boots, you will likely see a message about pressing
particular key to get into BIOS (often it's F8, or ESC, or something).
Press it during that short boot-up window where it will respond to this
key. It will give you access to the BIOS menu. From there, it's
machine-specific, but is menu driven. Search for the option to set a
boot-up password.
