My 12-year-old just got an iPhone and I want to set up location sharing so I can see where she is after school, but when I try to add her in the Find My app it asks for her Apple ID password and she doesn’t know it-am I missing a setting or do I need to set up Family Sharing first?
Yeah you’ve basically answered your own question — you need Family Sharing set up first, that’s the missing piece. Once you create a Family Sharing group (Settings > your name > Family Sharing) and add her Apple ID to it, Find My will let you see her location automatically without needing to keep entering passwords.
If she doesn’t know her Apple ID password, just reset it through Apple’s account recovery while you have the phone in hand — since she’s 12 you probably set it up anyway and it’s in your email somewhere. 