The basic of overclocking is to change CPU ratio(42), CPU Core Voltage (1.2-1.25V depend on stability).
You can read more here: http://edgeup.asus.com/2016/06/17/broadwell-e-overclocking-guide/

Raja's Broadwell-E overclocking is a very good place to start to maximize the performance of your CPU.

If you're interested in overclocking your GPU, I have a quick guide for doing so in my signature. 🙂

use the built in overclocking software 🙂 download AI suite 3 and open it up and overclock it there, the computer automatically tests until it becomes unstable and goes back to the best stable overclock, I had 4.3GHz from my 6800K stable clock, but 1 thing is to check the core voltage afterwards, mine was 1.5V which is like burning a candle at both ends, it will run fine but the processor will burn out fast, I got mine down to 1.35 @ 4.3GHz after some personal tweaking after the overclock. after a bios update though I had to RE-overclock the processor and went to 4.0GHz stable. I have had no issues playing any game max fps @ 1440p @ 144Hz

I found the software very nice for overclocking etc. also you can set your fan speeds too, mine don't even bother to do anything until my processor hits 60 degrees, which is never, my fans spin at 30% until 60 degrees then 50% to 70 degrees. highly recommended software, you will have a grin on your face when you see your cores go up and up, when I start my comp now it says ASUS ROG EDITION 10 20% overclock (was 33% until bios screwed me haha)