How do I add my daughters iphone number to my Find My Iphone?

I have a iphone 6 and so does she. I have already activated the Find My iphone app. How do I add her number to the app?

I've toyed with the idea of adding some bright red tape to the stems of the AirPods to make them more visually apparent in the snow, but I'm not sure how that'd affect their balance in my ears…

It's not related to the number (which is SIM related) but to the device and the ACCOUNT, the phone is on. In order to use find my phone to locate your daughters iPhone, you would need FULL access to her apple accounts.

If you want this access for nefarious reasons, then be aware that if you ever use it, then the phone makes it plainly obvious that it is being looked for/traced!

You can use the version on the Apple web site via a normal PC, if you log in to her account.

Details here:

As another answer says, it's not the number that matters.
It's not a good idea to try it on a phone or tablet as the device will be linked to that account until you switch it back, which could get very complicated…

You need to use the same Apple ID on both devices. You other option, if she agrees to it (You'd be violating her right to privacy if she's over 16 and you try to do this without her consent) is for you to use the find friends app.

Thats not how it works. Find my iPhone is for your iPhone only.