i plugged in my stealth 450 in my alienware alpha but didnt play any sound my monite is a LG UltraWide 29UM58

[Lahthix]

i plugged in my stealth 450 in my alienware alpha but didnt play any sound my monite is a LG UltraWide 29UM58 How do I get the sound to work?

 

[popatim]

Did you put the headphones on?
Make the USB audio the primary/default playback device? (Rt click the speaker icon down by the clock)
turn up or un-mute the volume?