Need Help with a Naze32 Rev6 Board

Just got a quick question:
I am trying to flash my Naze32 Rev6 board, but I keep getting the error, "Failed to open serial port." I know utterly nothing about these things, and would really appreciate some help! If needed, I can send screenshots and provide more details.
Thanks!
 
I am using Cleanflight. But the drivers thing is new... After reading the other article, I would think that that is my problem, because I never installed any drivers. Which drivers should I get? I am running Windows 10 on a 64 bit computer.