Depends on how it is shipped. The retailer (Walmart) should provide a tracking number and which carrier they are shipping. If USPS and UPS, they will generally knock and leave it at the door or place it in your mail box. Provided Walmart has not requested
a signature confirmation that you received it. If FedEx, they will likely require a signature. Some carriers require a signature on items of significant value, for instance $50+.
USPS will leave it in your Mail Box... If you Mailbox is too small than they may knock on you door to hand it too you or (like my lazy mail man) just leave a notice of delivery slip stating you need to go down to the post office to pick it up.
UPS tends to leave it at you door step or other "safe looking" areas if you home or not. (but they always knock first to check)
Never used Fedex... so I can't comment on them. Is DHL still around??? If they are they pretty much did things just like UPS does.