|It looks strait forward to me:|
Go to website displayed on the box (e.g. http://us.norton.com/walmart-n360md )
The website explains what to do. In case of PC-users (on above link):
Norton 360™ Multi-Device includes Norton 360™ Premier to protect your PC
3 quick and easy STEPS to get you up and running fast:
Click the "Download-PC" button and you will be prompted to save an .exe file to your computer. Begin download. We recommend you save this to your desktop so you can find it easily.
After the download is complete, locate the file on your computer and double-click it to begin installation. Follow the onscreen instructions.
When prompted, enter the Product Key which is displayed on the back of the card you purchased in-store. For help finding your product key, click here.
Clicking the 'Download' button will download the Norton installer file to your computer and to a location that depends on your browser settings.
Your Norton product key is theft-protected and must be validated at the register of the Walmart™ where the product was purchased. If you believe that your product purchase has not been validated, return it to the Walmart store with the proof of purchase and ask to have your Norton purchase validated. Click here for free Norton support.