 Hi NOLLEEE, Below instructions are from MacAfee website, this is what I even had done  Good Luck! 
I want to buy a Dell Inspiron Windows 8 laptop..  It comes with a 1-month McAfee trial.  I already have 11 months' McAfee Anti-Virus Plus subscription left on  old XP  which I will no longer use.  I am not computer literate so I thought I would keep the 1-month Trial Version on new Window 8 for a few weeks until I get used to the new OS. Would this be the correct procedure at the change over point?. 1.  Uninstall 1-month McAfee Trial version from new Windows 8 laptop. 2.  Download  my own McAfee Account on to  the new Windows 8 - click 'Deactivate' the old XP  and then click 'Download'  in order to put the Anti-Virus Plus on to the Windows 8. 3.  Then, uninstall Anti-Virus Plus from old XP.  Your advice would be much appreciated.   
Windows 8 and McAfee Firewall