If you are unhappy for whatever reason with your purchase from Walmart, you should have a read of their Returns Policy before shipping your items back, as returns policies are subject to change.
If you wish to return your item to Walmart using mail, click on 'My Account' > 'Track Orders' > 'View Details' - then click 'Start a Return' and from here you will able to obtain a free return label.
Then simply package the item in the original packaging and mail as per the instructions on the site. If you need some further advice on packaging your items you can learn more here.
Once the item has been processed by Walmart at their returns facility a refund will be issued. You can also return items purchased online instore as long as you have the original packaging.
Generally, items purchased on walmart.com can be returned or exchanged within 90 days. Items purchased from other companies via walmart.com will need to be sent back to the seller of those items.
Some items need to be returned more quickly such as cell phones and various other electronics which is outlined in the Walmart Returns Policy.
In terms of refunds, you should try and keep a copy of the receipt as it is then easier to obtain your refund. If the item was purchased using a credit card, any refund is issued to that same credit card.
If you need to book a courier service to return an item to a retailer, why not use the Parcel Monkey shipping calculator?