Place it just after the setup line in a short edit, then follow it with Vine Boom to underline the reaction, or open with Dun Dun Dun before that line so the payoff lands harder. Pair it with SpongeBob Fail when the moment is a clear on-screen mistake.
About this sound
This clip is a single human voice stretching the syllable fah into one long, drawn-out vocalisation. It lands as an exasperated reaction, with a dry, weary edge that makes the listener picture someone giving up on explaining, and it works because the delivery stays slow and unhurried throughout.