iPhone locked to owner

You need to recover access to the Apple ID you used to enable find my on that device.

If you can’t remember the ID or password, you can start here: https://iforgot.apple.com

Failing that, you can contact Apple and provide them with the original proof of purchase from an authorized retailer.

If you can’t do either one, toss it in the recycle bin at your local electronics store. There is no way to bypass the activation lock. You need either the account it’s locked to or the original receipt.

You have encountered activation lock. A theft deterrent system designed to make a lost or stolen device useless to anyone but the rightful owner.

Only the owner of the account used to lock it can remove the activation lock.

Assuming you bought it used, contact whoever you got it from. They did not properly prepare it for sale.

KiltedTim summarized it accurately. This Support document contains a few links that are relevant to what he said.

How to remove Activation Lock - Apple Support