New graphics card having problems

So I recently built my first computer. I don't understand most things I just followed a tutorial I'm not going to lie. So my graphics card was late arriving, so I tried to use the video card settings or whatever on the motherboard, just to install stuff first you know, but I always got a 'your computer may be asleep, please turn it on...'Etc as if no signal was found. Then when the GC came I put it in, it's a sapphire HD 7790. I put it into my computer and plugged the dvi-i into the monitor and the other end into the gc. I turned it on. Again with the same message as before, ' your computer may be asleep ' etc. So I tried plugging the blue cable, I believe its the vba cable, into the monitor and into a dvi-i adaptar then into the graphics card. Same message coming up. Help please:)