Get a Bitcoin wallet. You can read the reviews to find what you really need.
P2P exchange. Select the person-to-person marketplace. The system will pair your location with that of sellers in the area nearby. I would suggest LocalBitcoins or Paxful (the fees are a bit expensive here). You can buy BTC with online transfers, debit/credit cards, gift cards, and in cash deposits, which is the category that Walmart2Walmart transfers falls under.
Choose the amount of Bitcoins you want to buy and enter your email to sign up.
Select your payment method for cash deposits. Then you will see a list of payment options on the left hand side of the page in which you will see Walmart2Walmart listed.
Drive to Walmart to deposit the cash, and have the money transferred to the seller’s Walmart. All the information you need as far as where to transfer the money will be listed on Paxful.
Verify the transaction by uploading the receipt you got from the teller at Walmart.
The seller will release the BTC to you within 3 hours, perhaps even in as little as 10 minutes. It depends on the seller.