If your fans are connected properly, to either the fan hub located on the backside of the motherboard tray portion of the case where you have space for cable management (Backside, under the right side case panel. Take the case panel off and it should be there or may have been part of the hardware kit that came with your case and needs to be attached to the case in the area I mentioned. It's only about an inch to an inch and a half square with several fan headers on it. Instructions for using it are included with the case manual.) or to the motherboard headers, you should in either case be able to control the fan speed from within the bios.
The motherboard manual outlines configuring fan speeds in the PC health status section of the...