Help! My new PC won't connect to displays!

I just finished building my PC last night, and everything seems to be working fine; fans are on, I can hear the system boot up. But it won't connect to displays! I thought it was because my new monitor needed drivers, but then I tried using a different monitor, to no avail. I probably missed a step when connecting all the cables, but this is my first time building a PC, so I need help figuring out what I missed. Does anyone have any ideas?

I had the same problem with my new PC 2 days ago, and it turned out that I forgot the 4+4 cable that gives power to the CPU.

I stopped counting how many PC's I've built and still make that mistake occasionally, so I can imagine that a first-time builder could forget that too.

Whoa, I think that's actually what I forgot to do! I will update momentarily. Thanks!

Okay, I found the cable, so I definitely haven't connected it. But I can't find where I'm supposed to connect it on the motherboard. I have an ASUS Z170 pro gaming mobo. I've been looking in the manual to try to locate it, but I'm not sure where it is at this point.

Top edge of the motherboard, where the 2 black and red heatsinks around the CPU would intersect.

Okay, I connected it and it's still not working.

Are you using onboard graphics or do you have a discrete card?

What's the monitor doing when everything is plugged in?

I have a Sapphire Radeon R9 930 Nitro. The LEDs on the motherboard light up when the power supply is on or the computer is powered on.

The monitor switches back and forth between "analog" and "HDMI", but doesn't display anything. It's a 24" Samsung 1080p monitor.

Ah yeah, that's a nice card!

So from what I gathered you're plugging directly into the 390 with HDMI?
Do you have the specific model for the monitor?

No, the card itself doesn't have an HDMI port, so I plugged the HDMI into the motherboard. The monitor's model number is: S24D300H.

It is the Sapphire 390 Nitro right? It should have a single HDMI input

What CPU do you have? It might not have onboard graphics at all!

Wait, nevermind! Yes it does have an HDMI port! I'm going to try that really quick.

My CPU is an Intel i5-6600K.

Ah, it does have onboard graphics so it's weird it doesn't receive a signal on the mobo.....

Let us know how you go with the 390 HDMI

It worked! I'm so happy! Thank you, thank you, thank you!

No worries man, 9/10 it's the simple stuff that we trip up on like @CaptainChaos said haha

Enjoy the new rig man, it's a beast!

Thanks! I totally will!