I have a Dell monitor only that I want to use as a tv. Via the monitors hdmi port my Chromecast is plugged into I am able to

[txmimi70]

monitor only, no mouse or keyboard . the only audio source i have is an soundbar with red & white jacks . what does the blue oval with 15 little holes named?

 

[jsmithepa]

All I hear from you is, I have this car but it has no wheel, no engine, no seats... is not clear at all from your mumbled post. Think straight and post again.

 

[americanaudiophile]

If you gave us the model number we could check for you. You can't connect the soundbar to a 15 pin D sub connection.
If the monitor doesn't have an audio output you won't be able to get audio to the soundbar.
You could get an HDMI audio extractor to do that.