Open the Find My app on another Apple device, or go to iCloud.com/find on a browser
Sign in with your Apple ID
Select your missing iPhone from the list of devices
View its location on the map
Tap Play Sound to help locate it nearby
Tap Directions to get navigation to its location
Turn on Notify When Found if the phone is offline
Use Mark As Lost to lock the iPhone and display a message with your contact information
If needed, erase the iPhone remotely to protect your data
Keep checking the Find My app for updated location information