Hi there, rikk008. I understand wanting to enable Find My iPhone, so I'm happy to clarify. Please note that you can only enable Find My iPhone from the device itself. May I ask what happened with your phone?
how to remotely turn on "find my iphone" iPhone SE
You have to turn on find my phone on the phone, before you lose the phone. There is no option to remotely turn it on. It is possible your phone can still be located if you use find my iPhone on another device by signing into your iTunes account