Do you have an unlocked system with an unlocked CPU? These features are usually locked if you computer does not allow overclocking, these would be available in unlocked systems only. You can add you computer information so that we see what king of system you have.
Actually, i have no idea, because i bought this computer from the electronic shop.
My computer info:
Intel(R) Core(TM) i3-3240 CPU @ 3.40GHz 3.40 GHz
4 GB ram
Dedicated Intel(R) HD Graphics 2500
x64 Windows 8.1
Please note me, if something is missing.
This option is only available for unlocked processors