Open FSX and go to the "Addon" menu
Go down to "Addon Manager" and click it
When the screen opens on the left make sure "GSX" or "GSX Services" is selected and click on "Register Serial" at the bottom
Now enter your serial number that you received by email and click "OK"
You should then be asked if you are sure you want to activate just click "Yes" to both popup windows
Now wait a few moments and you should receive a message to say that a backup file has been created
Just click OK and now enjoy GSX
