Q: Bought iPhone 6, locked out with apple ID

It requires the Apple ID and password of the previous owner. If you don't have it and cannot get it, then the device is useless to you. Return it for a refund, if you can, or take it to an Apple store for an exchange provided they will help you.

Find My iPhone Activation Lock

In the future check first before buying second hand: How to check for Activation Lock before buying a used iPhone.

Then you have a useless iPhone. Return it if you can and get your money refunded unless the seller is able to fix the problem for you.