Reading online, I have found out how to redeem your digital copy. Apparently this is part of their Instawatch program, a less-than-elegant way of getting Vudu movies by purchasing movies from Walmart. It is confusing and not intuitive, despite their website saying it's "easy".
Here's how it works:
Step 2: Under your Walmart account, you will have to link to Vudu.
Step 3: Download the Walmart App on iOS or Android. If you do not have a mobile device: I believe you are out of luck.
Step 4: On your App, under "Savings", take a photo of the QR Code, or if you have a crappy camera like the Moto E phone, you can key in the "TC#" of your Walmart receipt.
Step 5: If valid, your movie(s) will now appear on your Vudu account.
Anyway, I hope this helps you if you weren't given any Vudu codes on your Walmart DVDs or BDs.