If you need to disable UEFI boot option from the BIOS to be able to boot from USB any linux system that the windows 8 default settings don’t allow, you basically need to follow 3 simple steps:

1. Press Shift while you click in the icon that looks like a power button and without release it select the option that says Reboot
2. You will enter in a menu, select the option “Solve Problems” or “troubleshooting” and then search for UEFI settings option if you have it, or “boot options” or something similar
3. It will reboot your computer, then it will automatically enter in the BIOS or you need to enter on it by using the F1 or ESC key (maybe is another key in your computer, read the boot messages, it is not possible to enter in the bios if you don’t do the previous steps).

Now you just need to browse inside your BIOS settings and mark these options, they can look a bit different in every computer, some ones don’t even exists, and you need to change these settings:

• disable “secure boot“
• disable “UEFI mode“
• enable “legacy boot“
• enable “CSM“

Save the settings and reboot your computer (probably the key F10), maybe you need to run the Boot Menu in order to select the USB to boot from, How to open the boot menu check our other FAQ link for this.

Important: Some computers can only boot from one of their USB ports, you should try from all of them if your boot fails.

Some nice articles with more details:

• disable uefi and secure boot in windows 8 – itsfoss.com
• disable secure boot in windows 8 – maketecheasier.com