USB BIOS update walkthrough

On my first build. Used an ASUS motherboard that didn't recognize my mini DisplayPort connector on my video card and I sent it back as much for their non existent customer support as the port defect. Put feelers out with good experienced people and it was suggested that ASRock would be a good place to go. They were so right. First, the computer fired up perfectly. Second, I know there is a community of ASRock user out there willing to help out a noob like me. Now that I've got it running and into BIOS the next thing is to do a USB BOIS update which is something I've never done. I'm writing this on my old computer, the new one doesn't have Windows and isn't connected to the internet. Can someone please give me a walkthrough of what I need to do, what files do I need, can I use any USB drive, and does it matter which port on my new computer I use? My new ASRock motherboard is a Z170 k6. I have never worked in any BIOS/UEFI before, if the computer worked I never messed with it. This is the first time I've built my own computer, it's the first time I'm going to try overclocking and it's the first time I'm going to run an SLI video card setup. BTW the LED display on the motherboard says A6. I don't know about that though the BIOS seems to recognize both installed but completely empty drives. Also I don't know where to find what version my BIOS is. I really appreciate that ASRock has made the effort to run this forum and thanks for whatever help you can give.

My motherboard is the basic Z170 Gaming K6 without the front panel USB 3.1. My BIOS version is P1.20, thanks.

I meant Version 1.3. Sorry.

Thanks, I'm now running V1.3. It startled me when it defaulted to the EZ mode which I hadn't seen before. Where can I find documentation about the changes from V1.2? I still have that A6 alert on the LED. Also one of my fan status indicators is showing the fan speed jumping around every few seconds, sometimes up to 20k RPM. I'm going to install Windows 10 next which I guess should be pretty straightforward. I think I'm going to be on this forum quite a lot in the next few weeks as I learn about my new hardware. I have found the PDF tutorial and it seems quite a bit more extensive than the manual that came with the motherboard. Thanks again for your help.