Changing your billing period will differ depending on the platform you used to purchase Universe Pro.
You will first need to let your current subscription expire (after cancelling it). To cancel your subscription, check out this article.
After your subscription has expired, you will be able to unlock Pro under a different plan in both the iOS app and the Web Editor.
🌟 You might have some issues if you have a custom domain. Please contact support if you are having issues with your custom domain after upgrading to an annual subscription. Chat us from the Universe app or send an email to help@onuniverse.com with your domain name and let us know that you upgraded from monthly to annual.