tap04950 It's actually worth installing yesterday's update if only for the performance improvements. You can switch back to DirectX 9 if DX11 mode isn't working for you; the setting is in the game options.
BIOS stands for Basic Input/Output System. It's the software for your motherboard and is more basic and fundamental than your operating system. It governs settings like how fast your RAM runs and boot order for your drives and the voltages supplied to your hardware.
To boot into BIOS, you restart the computer and immediately start pressing a certain key until you see the BIOS screen. Which key depends on the board; for Asus, I think it's F2 or F12. If you see the Windows lock screen, restart and try a different key.
Having said that, it's not a good idea to go poking around in the BIOS unless you know what you're looking for. So I'd suggest consulting the documentation that should have come with the motherboard or your computer. You may also be able to find a YouTube tutorial for your exact board if you search by its part number. And since this can be a bit complicated, I'd suggest updating the game and playing with the DirectX settings first.