The link provided is just for you to choose which plan you would like but then you need to enter my code to get the offer during sign up, the code is valid for all plans. Once you choose your plan you'll be prompted to enter your email address (do not use express checkout with Apple Pay or Google Pay), there is also an "add coupon" button on this page but the code does not go in there. On the next page there's more information to fill out including the "referred by a friend" bit, the code (calum8312) goes in there, and never expires :)