Windows probably wouldn't detect the card until after the drivers are installed, in case you haven't installed them yet.

You can enter your BIOS by pressing a key during your computer's boot sequence. It usually will display which key that needs to be on the screen. Usually it's delete or F2. In the BIOS you'll find heaps of settings - as a general rule of thumb, if you don't know what it does, leave it as it is. You just need to disable your onboard graphics in there.