No need to post everywhere. Normally you would enter the code on the website on that card, maybe on the back of the card.
You can use the below link to activate the corresponding McAfee product using the Key provided. Alter your country using the drop-down menu accordingly.
http://www.mcafee.com/mtp/retailcard (McAfee Total Protection)
http://www.mcafee.com/mis/retailcard (McAfee Internet Security Suite)
http://www.mcafee.com/mav/retailcard (McAfee Antivirus Plus)
Once you activated the product you can use the below instruction to login to McAfee account and install the products.
or for the RetailCD version:
http://www.mcafee.com/mav/retailcd for mcafee virus scan plus
Redeemed the product key. Log in if you have an existing account with mcafee if not click register now.
Do the onscreen prompt to download/ install.
If you have a problem call Customer Service. The number for your area is a free call: 1800 807643