I have the same motherboard, but a different power supply (Silencer MK III). That is where I plugged the two 4pin connectors that came already attached to my PSU. The plug is on the upper left of the Extreme 4. Good luck. I am in the finishing stages of my first build as well.
Thanks for answering
I've located the 12v atx power header on the mobo but which cable from the psu goes into it? The only ones I think could work are two 4 pin connecters (2x2 dimensions per connector right?)
(same as you) but do they have the label " CPU " on them?