How to connect speakers to computer through monitor?

[Thunderboltcat]

I have connected my computer and PS4 to a monitor and speakers, and the speakers were connected to the monitor, and it worked great, but now, i can't get sound through my computer anymore.
I have tried setting the external speakers as default, and all of that but it don't work..
Is it any other possible ways to connect them all together agiain?
(I still get sound when i use my PS4, so the speakers are proparly set up)

 

[digitaldoc]

How are the speakers connected to the monitor?

 

[Thunderboltcat]

How are the speakers connected to the monitor?

The monitor have a minijack input on it, so i just plug it in that. ( I have connected it into the Optical plug, not digital)