Put it near the end of a big reveal, after a slow build and a Dun Dun Dun beat, then follow it immediately with a Vine Boom to underline the payoff. That order gives the surprise a setup, a peak and a punchline without crowding the edit.
About this sound
This is a very short human scream, lasting about 0.6 seconds, that rises into a drawn-out, wobbly 'rrrwoahhh' with a processed, voice-changer edge. It feels sudden, over-the-top and comic, like a tiny panic attack played for laughs, and it lands best as a quick jolt rather than a sustained scare.