Hi Margot,
it's a real pain when this kind of thing happens, especially when it's your first attempt at putting a PC together.
Sorry to do this to you but, I would recommend you go back to the beginning and start the build process again. Do NOT remove the CPU from the motherboard, you shouldn't need to go back that far but remove all of the cables you have attached and remove the motherboard from the PC case. Put the motherboard on top of the box that it came in.
If you have a quick look through this article:
https://www.scribd.com/document/43985093/Ga-890fxa-Ud5-Review it will show you the basic steps of putting a PC together outside of the PC case. Although this is a pretty old review, the testing process is the same.
As you will have noticed, I use a set of switches that I have, but you can connect the power switch from the PC case onto the correct pins on the motherboard instead. Do NOT connect any other cables from the PC case at this time.
So, your basic setup should be as follows:
Motherboard with CPU and CPU fan attached. (sitting on a cardboard box)
One stick of RAM
24 pin ATX power connector from the PSU connected to the motherboard.
8 pin power lead from the PSU to the CPU socket. Make sure that you are not using a lead that is meant for the GPU.
Your GPU and any power lead(s) that it may require.
Monitor connected to the GPU (not the port on the back of the motherboard).
Mouse & keyboard attached to the rear USB ports.
Now try to power up the system using the switch on the PC case.
Make sure that you have removed the Corsair drive too.
Does the PC start?
If it doesn't double check that the basic cable connections are firmly attached at the motherboard and to the correct sockets on the PSU. Also double check that you have correctly connected the power switch from the PC case to the motherboard.
Now try to start the PC again. Does it start?
Check the diagnostic LEDS on the motherboard? Are any of them lit and, if they are, which one(s) as this will indicate where there is a problem. If only one lights up and it is the BOOT LED then the system has started properly.
If you are still not getting any signal on your monitor, can you connect it using the DVI-D DL socket from the GPU instead of the HDMI lead? If you can, shutdown the PC, connect monitor this way and try to start the PC again.
If the PC does start up correctly then great, we know the issue is with the HDMI connection which can probably be resolved later on.
You can start putting it back together in the PC case, making sure that there are the correct amount of stand-offs and nothing is sitting under the motherboard that may cause a short circuit.
If the PC still doesn't start then please post back with your results.
