You need to contact Visible customer service. Since you just joined today they should be able to add the promo code. If you are having troubles with chat, answer something else to a couple of the questions and when the chat box appears type agent, it should ask if you want to speak to a representative, answer yes of course.
There are other ways to contact them by messaging them on one of their social media platforms. For more information on how to contact them click the link below.
https://www.visible.com/help/contact-us
