Purchased a refurbished IPAD through Wal Mart (Big mistake) and it's locked which of course makes it useless. How do I unlock it?

You will never be able to use it without the Apple ID and Password of the original owner. Take it back to Walmart and get your money back.

If you want a refurbished Apple product, I strongly suggest purchasing from Apple in the future. As the other commenter says, you should return it.

The best place to purchase a refurbished device is from Apple, it comes with a warranty, and is refurbished by Apple. Any place else you have no idea who has refurbished the device and where they got the parts to refurbish it, since Apple does not sell parts. See this link, as the available devices changes constantly. https://www.apple.com/shop/refurbished