How can I find another iPhone from my iPhone?

Read this link please:

Apple - Find My iPhone, iPad, Mac, and Apple Watch - http://www.apple.com/icloud/find-my-iphone.html

"The new [iOS13] Find My app combines Find My iPhone and Find My Friends into a single, easy-to-use app on iOS, iPadOS, and now macOS.* Find My can help you locate your devices and your friends and family. And now it can help you find your devices — even when they’re offline." A good list of the features but otherwise contains few links to articles describing how to use the features. Those are better linked in:

Use Find My on iCloud.com - https://support.apple.com/explore/find-my

and:

Set up Find My on your iPhone, Mac, and other devices [iOS13 and Catalina] - https://support.apple.com/HT210400