Place it immediately after the reveal in your edit, then follow it with a short reaction shot so the moment can settle. For a bigger build-up, open with Law and Order Dun Dun before the reveal, and save DJ Airhorn for a later punchline in the same video.
About this sound
This 3.5-second clip captures Chandler Bing shouting 'Aaaaaaah, my eyes, my eyes!' after walking into the bathroom and finding Joey there. The high, panicked scream is pure comic horror, the sound of someone desperate to unsee an awkward moment. It comes from Friends, where his over-the-top reaction turns an embarrassing interruption into a lasting reaction sound.