In AMD Radeon™ Software, under the Gaming > Global tab there is an option for changing the clock and fan speed. You must enable AMD OverDrive™ and agree to the terms and conditions for this feature to become available. Once you have chosen your desired clock and fan speed settings, click apply.
If the manufacturer has customized settings for the card, the option for changing these settings may be disabled in AMD OverDrive™. In this case, please use the performance tweaking software provided by the graphics card manufacturer.