help locating lost phone

My daughter has lost her phone, find my phone is not active so I can't located it. I thought I could go onto the iCloud and turn it on there but the device doesn't not show on my iMac, its an old phone. So I don't understand why its not coming up on my iCloud, and I have no idea how to go about location this phone.

If it is lost how to I close all the apps on the phone