How can i locate an iphone

If you turned on Find My in the phone BEFORE it went missing and it is powered on and connected to a network, you can used the directions in this link to try to find it --> If your iPhone, iPad, or iPod touch is lost or stolen - Apple Support

If you did not have Find My turned on, you cannot find it by any means other than to look for it.

Are you talking about a lost or stolen iPhone:?--> If your iPhone, iPad, or iPod touch is lost or stolen - Apple Support

Are you talking about a different iPhone owned by a friend or relative?:--> Set up Find My on your iPhone, Mac, AirPods, or other devices - Apple Support

Regards

Giulio

The Find My app if you enabled it.