I can't seem to figure out how to plug my R9 290 GPU into my Corsair CX series 750 watt Modular psu, I got some cables with the GU itself, 1 8 pin and 1 6 pin both splitting into 2 Molex connectors. In my modular psu, there are 6+2 pci-e, 4+4 cpu and the peripheral + sata ports. I don't know where to go from this and have been stuck for quite a long time now. I am a bit of a pc building noob and this is my first build, please help!
Your Graphics card needs an 8 pin and 6 pin connection. Usually power supplies like that have 2 8 pin PCI-E connectors (Usually 6+2 each) just plug those into your GPU, the extra 2 pin on the second connector is just there for more high end graphics cards so just leave it hanging. The CPU connector goes into the top left corner of the motherboard.