Use Find My only if the person has shared their location with you
Open the Find My app on your iPhone
Tap People
Select the person from the list
View their location on the map
Use Messages and tap their name or profile at the top if they have shared location there
Ask them to share their location with you through Find My
If you are in a Family Sharing group, check the Find My app for family members who have enabled sharing
Use iCloud.com/find only for devices linked to your own Apple ID
Contact the person directly if they have not shared their location