Most Motherboards provide fan control via the BOIS, and they are above the bare bones budget level, via a MoBo Utility, both of which should be well described in the motherboard manual. Most mass market PCs are light on both features and manuals and go with less MoBo features as it adds to component and support costs.
The the MoBo is not so equipped, reading the manaual and perusing the BIOS should answer that question, your other options would include Speedfan and a manual fan speed controller. You should also check and see if the fans are connected to the MoBo or direct to PSU. This is one of the most useful and full featured manual controllers and available at a reasonable price...