I think you need to provide more information regardingy your setup.....
I.e., how are your speakers currently connected? Do the monitors have speakers?
Generally the monitor(s) are set up via the graphics card. The speakers via the audio card.
But if you are just using extended monitors along with audio via the sound card then the speakers would just be plugged into the sound card.
Use the small speaker icon (usually lower right screen corner) to set up the sound via "Playback devices".
Monitors are controlled via a right click on an open area within the desktop.
Overall it is probably best if you just set up the visual and audio as you desire/require. Then, if it does not work, post the details and the problem that you are encountering.