Welcome to the Magix user to user forums. As such, no-one here can help you directly but we can offer some advice, perhaps.
First, where, exactly, did you purchase SFACL2? If it was direct from Magix you should have received almost immediately on completing the purchase, an email which includes the download link and the serial key. If you did not receive this, have you checked your Junk/Spam folder?
If the purchase was via a third party you will need to ask them about the missing details you need.
In the meantime, if you have not already done so, you can download the Free Trail version of the software from here. Once you have your serial key you can simply enter it to fully activate your program.