I'm assuming this is a monitor with speakers built in? If so did you connect the audio cable between your sound card and monitor and into the right jack, usually green?
If that isn't the case and you have separate speakers you could try a monitor driver(99.99% of the time aren't needed).
If it is a monitor w/ speakers there may be some software you need for the monitor speakers(doubt it) or on the monitor there ought to be a menu button and in there you may simply need to enable the speakers and they may be disabled by default.