To activate McAfee on Windows, double-tap on its icon. If prompted enter the login details of your account. Enter the 25 digit McAfee activation code to proceed further via mcafee.com/atcivate . To activate on Mac, use the Finder and locate its icon. After this, double-tap on it. On the next page, enter your Mac login details. Enter the serial number of the McAfee products. Congratulations! McAfee is activated on your device.