Walmart hasn't adopted Apple Pay, and it's not clear whether it will (though one report I read said the company is increasingly open to it). Now, however, you have another option for paying at Walmart. Last week the company launched a new mobile payment system at selected stores that lets you pay for your purchase at the checkout counter by scanning a QR code with your iPhone or iPad. (For it to work on an iPad, though, you'll likely need to have a cellular data model.) The new mobile payment system will be available nationwide by the first half of next year.
How does it work? When you're at the Walmart register you open the Walmart mobile payment app and choose Walmart Pay. You then scan the QR code displayed at the register. That's it. When the clerk is done scanning your items and completes that transaction, an eReceipt is sent to your Walmart app.
According to the press release, Walmart Pay is available on any phone that can download the Walmart app. It works with any major credit, debit, pre-paid, or Walmart gift card. And if you have Touch ID, you can use that for greater security.
If you have an iPad, note that Walmart has "retired" its iPad app, but you can still download the iPhone app to your iPhone.