Hey there,
You can enter the promo code given by GiveawayoftheDay by opening SecureAPlus > Info & Licenses > Account.
Instead of logging in, you can simply click on the green "Enter Activation Code" button. This will ask for your activation code (from GotD) and your account email.
For reference here's a screenshot:
http://imgur.com/a/YIXY5Note that if you have an existing SecureAPlus Account this will immediately upgrade your license to premium. If not you will have to click on the new account verification email sent to you so make sure you enter the correct email address (you might also need to check your bulk, promo, or spam folder in case it doesn't land on your inbox).
I hope you find this helpful and if the problem persists, rest assured that we will assist you in claiming a Premium License now that you have highlighted the problem during the giveaway period.