Go ahead and sign up for the free trial by inputting your info and clicking on "Register for Free Trial"
When on the main page, look in the upper right and click on the head icon to drop down your account menu. Then click on the "Subscription plan" Look at the bottom of the page and click the "Annual" radio button. Then click on "Subscribe" under the basic plan. In the window that opens, enter your country and zip, and on the next window click "Add Coupon" Enter your coupon code (INFOSTACK2019) and click on "Add Coupon" Then continue to check out as normal.