my iphone is lost, any way to use icloud to find it

If Find My iPhone is not activated there is no way to track it. But Find My does not require an app to be installed; it is an iOS function that is enabled automatically when you first set up the phone, as soon as you log into your Apple ID or create one on the phone. If you didn’t set up the phone initially when you got it, or didn’t log in to an Apple ID in setting it up then Find My iPhone will not work. Likewise if you turned it off. So what is your actual situation? If you think you set up an Apple ID log in to https://icloud.com/find using that Apple ID. Click on Devices, and if Find My iPhone was enabled you should be able to see its location (assuming its on and connected to the Internet, of course).

The Find My app is also built into the phone, it does not need to be added. But its purpose is to track OTHER devices, it isn’t what makes your phone findable.

No. If you didn't sign into your iCloud account on the device and activate the find my service, there is no way to track it.