Video card with only HDMI output?

My son was given a used computer recently and we can't get sound to work..the monitor is hooked up to the video card which instead of having the hole thing (sorry :))to plug speaker in it has an HDMI output..He needs that video card b/c it allows him to play certain games which the base one does not..previous owner was using for video streaming on his TV but used it regularly once w/ sound.said he thinks it must be a setting...? We have speakers and speaker via his monitor but neither will work..anyone know what we can do:?|||is the card installed properly on the computer? If not it might not work correctly.