Check to be sure a BIOS update is even needed first by going into the BIOS and finding the current BIOS version in the lower right corner of the BIOS screen..BIOS v1.09 is the latest so far for a Z170 Stinger..If you have an older version, continue.
Go to the
EVGA Drivers and BIOS page..In the Motherboard tab, enter the required information and Submit to show the list of BIOS'..Click View in the Notes column to the right of your OS..The BIOS download and simple instructions are there for either flashing in Windows or from a USB flash drive, either way you want to do it..There is really nothing complicated about it.