Why are you trying to flash your mobo? It's asking you for the BIOS file to flash with (the whole point of flashing is to replace your BIOS with a newer specific BIOS for your mobo). If you don't understand that, please stop right now. If you are not careful here, you are going to turn your mobo into a paper-weight!
First off, there's likely no need to update your BIOS on a new mobo anyway. You need to research the overclocking guides here and elsewhere first. You can post at 200mhz because you are massively o/cing a thoroughbred-core cpu. Also, what type/speed of memory are you running, and at what timings? Again, consult the guides ... o/cing without proper testing can easily lead to data corruption and a need to re-format your hard drive.