All our computers come with a sound card installed and sound should work from the start, if you have any problems with sound, run the program alsaconf as root (administrator). Open a terminal to access the command line and enter alsaconf to detect your sound card. Continue by hitting enter when prompted and your sound card will be reconfigured and you will be shown a friendly message confirming that this is so.
If you still do not hear any sound it is probably because the sound is turned down. Click on the loudspeaker icon in the system tray of your window manager and adjust the master output volume slider to your preferred level.