Open the Find My app on the other phone
Sign in with your Apple ID
Tap Devices
Select your iPhone from the list
View its location on the map
Tap Play Sound to help locate it nearby
Tap Directions to get navigation to the iPhone
Tap Mark As Lost if the iPhone is missing
Add a phone number and message if prompted
Use iCloud.com/find in a browser if the Find My app is not available
Sign in with your Apple ID on iCloud.com/find
Select your iPhone from All Devices
Check the device location and available actions
Keep location services and Find My enabled on your iPhone for future tracking