I need to find my iPhone

You can use the same Apple ID associated with the missing iPhone to locate the missing iPhone, logging in and using Find My from the iCloud website.

You can also use Find My on another Apple device you have already associated with the same Apple ID, and members of the same family configured for Family Sharing can also locate your lost device.

If Find My was not already enabled on the device, Find My cannot be remotely enabled on an already-lost device.

Click or tap on the following blue-text link for more info: Locate a device in Find My iPhone on iCloud.com - Apple Support

Aobrien771 Said:

"I need to find my iPhone: How can I locate a different device"

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A Different Device than what?

If it is a device that is not associated to your Apple ID, then using Find My is not an option in your own Apple ID.