Place it at the start of a spawn moment, just before the enemy becomes visible, then follow it with Enemy Spotted to name the threat. For a bigger scare, save the FNAF Jumpscare Scream for the moment the enemy attacks, after the spawn cue has set the scene.
About this sound
This is a short 1.2-second cue from The Binding of Isaac that plays when something spawns into a room. The sudden arrival makes it feel tense and unsettling, like a threat has just appeared beside you. It comes from the roguelike game, where the sound marks enemies and other hazards entering play.