In Studio One 2, you will want to go into Studio One>Options>Audio Setup and enable multi-processing as well as enabling your cores. If the cores are not showing up there, then more than likely, you are missing a setting in your BIOS. Go into the BIOS of your motherboard and make sure that you have enabled Hyperthreading. You might also want to check your Front Side Bus settings. For the i-series processors, the FSB (Front Side Bus) is normally set to auto so that it can turbo boost the speed. Depending on your motherboard, there may be a setting to enable all of your cores that you are missing in the BIOS. Make sure that the BIOS of your motherboard is up to date as well.
You might also want to check your power settings and see if you have core parking enabled. You may want to try disabling it. Here is a link to a 3rd-party web site with information on managing parked cores.