how can i factory reset my iphone locked to owner

Apple has two related features, Activation Lock ( Activation Lock for iPhone, iPad, and iPod touch - Apple Support ) and Find My ( iCloud - Find My - Apple ), which are designed to prevent anyone else from using an iPhone, iPad, or iPod touch if it's ever lost or stolen. Deactivation of either requires knowing the Apple ID and password that set the feature, or by placing a special request to Apple to reset the device. This Apple ID information essentially defines the current ownership of the device.

Click on this link to learn how to remove Activation Lock --> How to remove Activation Lock - Apple Support

or this one for disabling Find My if activation lock has not yet engaged --> Turn off Find My on your iPhone or other devices - Apple Support

If you do not know the required information and you are not the owner, get the owner of the account to remove the lock, or return the device for a refund, or recycle the device. The device is otherwise useless to you. If the owner is unknown and has not provided contact information as a message showing in the login screen, there is no way to contact the owner unless the person who gave you the device knows them.