Cpu Cooler, Case, or MOBO?

[Jetsetskyking]

I made a mistake getting a CPU cooler as big as a Noctua DH-15 with my latest build, I got a gigabyte z270 gaming 5 MicroATX motherboard, and a diypc skyline-06-B case. The biggest problem I have is not being able to reach a stand off to screw the mobo in the back top corner near the io panel I have because the case, a fan, and the giant radiator are an obstacle for my hand to place the screw. Also, my motherboard has 3 connectors for case fans, but I can see two more in front of the 3.5 drive bay slots, and I have no place to plug them up. the case supposedly has an integrated fan controller but admittedly I have no idea where that is or what it looks like, the case came with no manual, just some pictures identifying key and mostly external features.

 

[Aeacus]

Who said that your case has built-in fan controller? Official specs doesn't state that though,
specs: http://www.mydiypcusa.com/products/skyline-06-wb.html

As far as your other issues go, and if you want to mount NH-D15, best way to do it is when you breadboard your MoBo. It means that you remove your MoBo from the PC case, set it on any cardboard box and then fasten NH-D15 into place. Once NH-D15 is secure, just put your MoBo back into the PC case.

You say that you have a rad in the case. What use it has? To cool GPU?

With 3x fan headers on your MoBo, you can use Y-splitters to double the supported fan amount just fine with connecting 2x fans into single fan header,
Y-splitter at amazon (2x in the box): https://www.amazon.com/Noctua-NA-SYC1-Accessory-4-pin-Y-Cables/dp/B00KG8K5CY