MONTOR

Hello,
have recently just installed a new Motherboard,CPU,RAM, and a Graphics Card although the system boots and i go motion from all the parts i cant seem to get the screen from the monitor to show up which normally happens straight from the boot up i have checked the cables in the back of the graphics card are correct but this is the first time of a boot process so i need to access the screen to make any BIOS changes to the motherboard etc but the screen just wont come up plz help