Navigate to the main window of the program.
There should be an "Upgrade" button at the bottom.
If you click this button, a new window opens up with a big "Buy now" button on it.
Now you just need to click on the text below the button saying "Already have a serial number? Enter your serial number now" to reach the window where you can enter your serial number.
Enter your serial number and your e-mail address, with which you can register your product online in the next step.
If everything has worked out, a window will appear to show you that your activation was successful.
If your serial number does not fit into the specified boxes, please download and install this version.
Uninstall the old version before.