You can use a microphone and computer speakers or use a headset/microphone (preferred). Either way, you will need a speaking device and a listening device. For the headset you will see two jacks (perhaps red and gray/orange/green) at the end of the wire leading from the headset. These two jacks need to be inserted into the appropriate jacks on your computer
You can purchase a USB headset with microphone that can be inserted into a USB port.
NOTE: Some users have experienced issues with USB headsets such as delayed or interrupted sound. It is suggested that you only use a USB headset if it is the only headset to which you have access.