Hello
You should be able to turn it on. Go to the Overclocking settings tab. If you scroll down a bit you will see that CPU Voltage setting, it should be on Auto by default. You can change the value there. You should be able to see the current voltage settings in the same area but it would be different for each CPU. Here is a link to some screenshots and an overclocking guide:
http://www.eteknix.com/msi-970a-sli-krait-edition-motherboard-review/4/
Hope this helps