I still don’t understand how to use Find My.

First, make sure it is turned on as described below from: Set up Find My on your iPhone, Mac, AirPods, or other devices - Apple Support

1. On your iPhone, iPad, or iPod touch, open the Settings app.
2. Tap your name.
3. Tap Find My.
4. If you want friends and family to know where you are, turn on Share My Location.
5. Tap Find My [device], then turn on Find My [device].
6. 
7. To see your device even when it's offline, turn on Find My network.* 
8. To have the location of your device sent to Apple when the battery is low, turn on Send Last Location.

If you want to be able to find your lost device on a map, make sure that Location Services is turned on. To do this, go to Settings > Privacy > Location Services, and turn on Location Services.

* The Find My network is an encrypted, anonymous network of millions of Apple devices that can help you locate your device. 

Then, to locate the iPhone you can use any internet browser and log into www.icloud.com/find

or use other methods described in If your iPhone, iPad, or iPod touch is lost or stolen - Apple Support and Use the Find My app to locate a lost or stolen device - Apple Support

Find My on iOS devices is enabled in the AppleID settings on your device. Thankfully it is a feature that is now enabled by default (once authorized via a popup screen during setup.)

Settings > AppleId (at the top) > Find My > Turn the top option on.

You can then use the Find My app on another apple device you own or access the feature via www.icloud.com

Please explain what you "don't understand" after you review the "Related Article." Set up Find My on your iPhone, Mac, AirPods, or other devices - Apple Support