Video Card Problem - Can't change BIOS setting?

How do I change the BIOS setting from on board video to new PCI-E video card when monitor does not stay on long enough to find and change the setting? Monitor is black connected to new card and only last seconds connected to old on board video. Time gets shorter each time tried.|||Pull out the video card, and plug your monitor in to the onboard video. Go into the BIOS, change the setting, save & exit. Power down and plug the video card back in and plug the monitor back into it.