In the case of my laptop, which is from Dell, Dell itself deploys updates through Windows Update, and there's also instructions at Dell's website on how to manually update it using an USB stick. When the manufacturer doesn't deploy automatic updates, I believe there are somewhere instructions to do that, perhaps at the motherboard's website, and you can probably do it from your system, whether Windows or Linux.

I have a custom build tower, and I think that manufacturer would be Gigabyte then.