What make and monitor do you have?
What ports are available on the monitor? E.g., a headphone port? Did you use the monitor's configuration menus to enable any audio ports.
On your laptop, right click the small speaker icon and go into Playback devices.
Check all of the windows, tabs, and property settings.
Could be that all you need to do is change the default Playback device from TV to an audio port on your laptop.