I bought a PSU for the first time and found out that my motherboard needed a 4-pin ATX. But I only have 2+6-pins on the PSU. Here's the PSU; http://www.netonnet.no/art/NoSection/coolermaster-gm750wmodular/193226.7279/
The one you talk about is for the GPU only. You should see the one for cpu which is 4pin+4pins one. Here is from company website. http://www.coolermaster.com/powersupply/gaming-gm-series/g750m/ So you only need plug in one 4pins cable into the MB.
The images on the back of the box that the PSU came in should show you that the 4+4Pin CPU connector splits in half. Plug one half into the motherboard.