Go to the motherboard website.
In addition to the BIOS and info. being at the mobo maker's website, you'll need a functioning CPU to update to a newer BIOS. Your mobo owners manual should explain the process as well as some mobo makers have videos or written instructions on their website. It's extremely important to be 100% certain that you are installing the correct BIOS for your specific model and Rev of mobo as there can be many similar mobo models depending on mobo brand. The mobo maker's website should tell you the first BIOS that provided support for your specific model CPU. You can use that BIOS version or any newer one for your specific model and Rev mobo.