I've been trying to setup Ubuntu 14.04 (64bit) along with my Win 8.1 Desktop-PC. My Problem is, that I have UEFI instead of the normal BIOS. When I just install Ubuntu as I did very often on other machines, and start my PC, it boots right into Windows without entering GRUB. Well, after some research, I figured out, that I have to switch off secure boot in my UEFI. I found the following instructions.
On the second link, there is a point, where I am supposed to enter the UEFI-Firmware-Settings via Windows. The problem is, my Windows doesn't show this option. When I boot straight into UEFI, there isn't an option for secure boot or no equivalent either.
I am using an ASUS motherboard. My UEFI looks like this.