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/mtp/retailcd for MTP
http://www.mcafee.com/mis/retailcd for MIS
http://www.mcafee.com/mav/retailcd for McAfee Virusscan 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.