I bought a used apple iPhone 6 and it has an account from the previous owner what do I do I just found it

That's bad.

If that iPhone has "activation lock" (an anti-theft measure), neither we, just users like you, nor Apple can help you, sorry, unless you are the original owner and you still have the proof of purchase (receipt/invoice reporting your device’s IMEI or Serial Number). Should be this case, start your request using this link: https://al-support.apple.com/#/additional-support

Shouldn’t be this case, activation lock can be removed only by the previous owner, with the credentials that were used to activate that iPhone/iPad. Without those credentials, that device is useless to you.

You can also take a look at this support article:--> How to remove Activation Lock - Apple Support

Regards

Giulio

the previous owner needs to do the following

What to do before you sell, give away, or trade in your iPhone, iPad, or iPod touch - Apple Support

activation lock needs to be removed How to remove Activation Lock - Apple Support

if he don't know his appleID

Recover Your Apple ID - Apple

Demand your money back.

First time you need to reset it the phone will be lost. You will not have access to any iCloud assets. The previous owner may disable it or remotely erase it without notice.

Enjoy.