Assuming you purchased direct from Magix - did you check the confirmation of purchase email you would have received with your serial number in it? If this is a new purchase - they sometimes end up in your spam folder.
If you purchased from a store or other online seller then you may have received a voucher code in which case you can redeem the voucher here, you will then receive your serial number by email.
If you do not have the email then follow the instructions in the comments above.
Please do not type in all capitals, it is considered as shouting and is not good forum etiquette.
Did you order and pay for it direct from Magix? If so, you should have received an email confirming the sale, giving you direct access to the downloader and including your serial key. Did you not receive this?
If you did not or have deleted it since receipt you will need to do as previously advised and email email@example.com, taking care to use the same email address as you used to make the order, and ask that they resend this confirmation email. The serial key will not show in your account until you have successfully, installed, registered and activated it.