Hi Fxavier,
The promo code is to be entered after you have logged in from within the SecureAPlus Account. You reach this by going to Info & Licenses > Account.
From there you need to login using your SecureAPlus account and after successfully doing so you will land on the SecureAPlus dashboard from within SecureAPlus. This is where the "Promo Code" field is located.
As the promotion is already over, please drop us an email at secureaplus@secureage.com and we will help you from there.
Kindest apologies for the confusion and rest assured that we will improve this process in the near future.