3.8GHz is the max turbo frecuency for the Core i7 6850K, and thats for only 1 core. All core boost is 3.6GHz
Heres one of the best guides I know:
https://forums.tomshardware.com/faq/cpu-overclocking-guide-and-tutorial-for-beginners.3347428/
Here are two guides about OC on X99 platform:
View: https://www.youtube.com/watch?v=xvG31oiHZ18
and
View: https://www.youtube.com/watch?v=2h8jWBd0XL4
Keep in mind stable OC needs,
- Very good cooling, thats a 140W TDP CPU
- Very good PSU.
- Stable and compatible memory configuration. Preferably not XMP till you know CPU oc works fine.
You haven't give any information about your CPU cooler, nor your PSU (please give brand and models of both).
And also haven't mention what youve done soo far.
Keep in mind OC can eventually damage the CPU, specially if you do not know what youre doing. So do it at your own risk!!!