Place it at the end of a setup where someone is asked to agree, letting it act as the clear yes before the scene moves on. Follow it with Okay Let's Go to start the plan, or contrast it with Nope when a second character refuses.
Über diesen Sound
This is a short game voice clip of Mettaton delivering a bright, theatrical 'Oh yes' in just under four seconds. It feels gleefully approving and a little camp, like a showman giving an over-the-top yes to something he loves. The line comes from the Undertale robot showman, whose flamboyant delivery turns a simple agreement into a celebration.