How to find your iPhone using Find my app.

Below are links provided by Apple on how to use the Find my app and iCloud (on the web) to find your iPhone. 

https://support.apple.com/en-us/HT210400 (How to turn on Find My for your iPhone)

https://support.apple.com/guide/icloud/locate-a-device-mmfc0f2442/icloud (Locate a device in Find Devices on iCloud.com)