See: 
http://www.maketecheasier.com/disable-secure-boot-in-windows-8/2013/02/25

from which:

7. Once the computer starts up, you’ll need to access your BIOS. To do 
it, you have to press “Delete,” “F1,” or “F2″, depending on your 
computer, on your keyboard as soon as the computer begins its power-on 
process again. Try each one and see if it works. Usually, the key is 
revealed at the startup splash screen in a message that says “Press 
<some key> to Enter Setup.”

Note: Each BIOS configuration utility is different. You’ll have to 
intuitively navigate through the interface with my vague directions.

Note: You might not even find a secure boot option anywhere. You might 
not even find an option under “Security.” The below image shows the 
option as “UEFI Boot” under the “Boot” menu. Keep your eyes peeled for 
anything containing the words “Secure boot” and “UEFI.”

As can be seen, the ability to disable the secure boot is determined by 
the hardware (mainly the BIOS). While our hardware allowed us to disable 
the secure boot feature, that doesn’t means your hardware is the same. 
You will have to play with it and hope that it comes with the ability to 
unlock the secure boot.

End quotes.
On 09/24/2013 08:53 AM, Yasha Karant wrote:
> Secure boot is enabled.  Evidently, the only means to disable secure
> boot requires that a secure boot loader/configuration program be running
> -- e.g., the MS proprietary boot loader (typically, supplied as part of
> MS Windows 8) must be used to disable secure boat if the UEFI actually
> permits this to be disabled (I have heard of some UEFI implementations
> that do not permit secure boot truly to be disabled).
>
> If Linux cannot handle this issue, then Linux is finished on all generic
> (e.g., not Apple that supplies both the hardware and operating
> environment software under a restrictive proprietary for-profit
> intellectual property license) X86-64 hardware, as (almost?) all current
> such hardware is MS 8 (UEFI secure boot) compliant.
>
> Yasha Karant
>
> On 09/23/2013 10:29 PM, Connie Sieh wrote:
>> On Mon, 23 Sep 2013, Yasha Karant wrote:
>>
>>> A colleague who uses SuSE non-enterprise for his professional
>>> (enterprise) workstations has now attempted to load the latest SuSE on a
>>> machine with a new generic (aftermarket) "gamer" UEFI  X86-64
>>> motherboard.  It does not properly boot.  I do not have any UEFI
>>> motherboards, and thus no experience with SL6x on such motherboards.
>>
>> Is "secure boot" enabled in the UEFI ?
>>
>>>
>>> Does anyone?  Does SL6x boot correctly (and easily) on a UEFI
>>> motherboard?  If so, he may switch to SL.
>>
>> Yes as long as "secure boot" is disabled .
>>
>>>
>>> Yasha Karant
>>>
>>
>> -connie sieh