i lost my iphone what should i do

If you have Find My enabled, you can log-in with your Apple ID (The same Apple ID you have used to sign in here if it is the one linked to your device), you can do so here https://www.icloud.com/find

This allows you to

• Track the last known location of your phone
• Erase your device and lock the device so the potential thief can not use it
• Display a message with your contact details so hopefully, someone finds the phone and can contact you

The phone must be online, powered on and connected to some sort of data/wi-fi for this to work.