When go to the colorful manufacturer site, they don't post the manual, that means you maybe out of luck. But try look at the ASUS A68HM-K manual first, then boot into bios to see you can find the similar menu in the BIOS. If you can't find it, that means you can't oc.
The ASUS A68HM-K manual https://www.asus.com/us/Motherboards/A68HMK/HelpDesk_Manual/