It's illegal to do, and illegal to solicit, so make sure you turn yourself and Walmart in to the FBI if you do, but here's how...go to Walmart.com
and write the review, then take a screenshot of it. Then long press the URL at the very top in the status line. A flag should come up with choices to copy, or copy URL, or on some phones you may need to click the phones menu button to find copy URL. However you get it, it will be on your clipboard. Go to your email and paste that in. Add the screenshot for verisimilitude, and send it to them.