Put it right after the decision point, following a click that marks the choice and before the action that follows it. Pair Click Nice first to signal the selection, then this clip to confirm it, then Okay Let's Go to launch the next scene.
このサウンドについて
This is a very short voice clip, about a second and a half long, of a single word, “OK,” delivered in a bright, punchy arcade-game voice. It feels playful and satisfying, like a tiny reward for getting something right, and it works as a light, confident yes without any extra fuss. It comes from Metal Slug, the run-and-gun arcade series known for its expressive voices and sharp menu feedback.