Generally when you first turn the power on the manufacturer will have a message such as "Press F2 for setup" or "Press Del for setup". You briefly and repeatedly press the indicated key. You will then see the screen fill with all kinds of information about the motherboard.

There is usually an entry such as "Integrated Devices". Use arrow keys to highlight that then press the Enter key. You should see a list of the devices that are built into the motherboard. Next to each device is its status which with either be "Disabled" or "Enabled".

The bottom of the screen will usually have a message about how to change the status, usually by highlighting the status and using the + or - keys.

Once you are happy with the settings you can maneuver to the Exit at the top of the screen by using the arrow keys, then select "Save Settings and Exit".