i bought my iphone at a yard sale and cant get it unlocked can u help me

The various definitions of “UNLOCK” and I recommend that you pick one of the below that fits your request.

Unlock1: If you forgot the passcode to access the device: ➔ If you forgot the passcode for your iPhone, iPad, or iPod touch, or your device is disabled

Unlock2: If you forgot your Apple ID password: ➔ If you forgot your Apple ID password - Apple Support

Unlock3: Your device is locked to a different carrier and doesn't accept SIM cards from different carriers: only the carrier it is locked to can unlock it, if you're eligible.

Unlock4: If you have an Activation Lock, neither we (just users like you) nor Apple can help you, sorry.

Activation lock can be removed only by the previous owner, with the credentials that were used to activate that iPhone. Without those credentials, that device is useless to you.

Axel F.

If it is activation locked you will be unable to use it without the cooperation of whoever enabled the Activation Lock theft deterrent feature.

You need help from the previous owner if the phone is activation locked. It is useless to you without their help.

How to remove Activation Lock - Apple Support