I guess you are referring to X98Air3GDuala.bin part? If so, you can skip this part because BIOS has already been flashed by the host Windows PC.
If you are referring to clean install Windows 8/8.1, then sorry I don’t know. I asked a similar question here (http://techtablets.com/forums/topic/windows-8-1-image-from-teclast/), but I did not tried at the end. But according to Chris it is the BIOS really matters. I strongly recommend you follow Zeigar’s post (because I was not sure if the Chinese bat file shown in the video suits my C5J6 model). Yes it is a bit more complicated but you will understand better.
FYI I upgraded to Windows 10 first, to make sure it is activated. I then did a clean Windows 10 install. The drivers need to be re-installed are less than Windows 8.1.