My graphics card isn't detecting

I recently bought a new graphics (Asus GTX 950 strix) and a new power supply (Corsair VS350). I currently have a graphics chip that built into my processor (AMD A8 6600K APU). Firstly I installed the new power supply and then I put in the graphics card, I slotted in the 6-pin connector. I turned on my computer and in dxdiag it told me that it was still using the graphics chip instead of the graphics card. My vga cable is currently plugged into the motherboard, but when I put a hdmi into the graphics card it shows 'no signal' on my monitor. Can anyone please help?
Also my motherboard is a gigabyte GA-F2A55M-HD2
 
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