My first build , I have a asus b350 plus motherboard but for the hdd led it only has 1 pin on the mobo and the cable has 2. Already read the manual and no luck. Nor did the case came with instructions.
Well, try it with just the one pin, don't worry about using the HDD LED, or contact the manufacturer to make sure there is supposed to be a pin there and if so, return the motherboard as defective.