New Graphics Card not Working

[FireVortex720]

Hey guys,
I bought a Sapphire Dual X R9 270x and I tried to install it but it is not working correctly.
I first turned off my PC. Then I took out the VGA cable from my mobo and used the adapter in the box to connect it to the r9 270x. after that, i put the gpu in the x16 slot in my mobo and connected the 6 pin cables. I then turned on my PC, but all my monitor is showing is a black screen.
The fans on the 270x are spinning, but the monitor is black.
This is my first gpu, any help would be appreciated!

 

[njxc500]

Were you using onboard graphics before?


You may need to enable this in the BIOS, or possibly disable onboard graphics.

 

[Greg Gregorich]

it depends on gpu,but you may need connect power cables to gpu,ifno bueno then just clear cmos.

 

[FireVortex720]

Were you using onboard graphics before?


You may need to enable this in the BIOS, or possibly disable onboard graphics.

Yeah that was it haha.
I took out the 270x and went back to BIOS and changed the preferred graphics adapter and it worked. Thanks!