I would say best to call customer support and get them assist you
Services and Support for Home and Office
Also post what product you have and the Operating system and service pack. Each product has its own retail card activation FAQ and things appear to have got messed up somewhat.
The below is what should have been done
You can use the below links 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 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.