Click the My Account icon top right of the home page
Login with the email address and Password you used to register the program with
Select My Products
There should see your registered product(s), and your serial number and a download link.
. . . . I purchased my Magix with a laptop . . . .
If this was pre-installed on the laptop and you did not have to register it then there may be no record of the software in your account, in which case you will have to purchase it unless you have a recovery disc for the laptop.