In your HubSpot account, click the settings icon, in the main navigation bar.
On the left sidebar menu, navigate to Website > Pages.
Under the System pages tab, you will see all types of subscription pages.
Use the dropdown menu to select the right template.
You can search for the theme name as a keyword when selecting the dropdown for easy search for the template that you want to use.
e.g. On the 404 error pages, we searched the outlook keyword and the outlook 404 system template showed up.
Hit Save once you’re all good setting up the pages.
Reference video: https://share.vidyard.com/watch/Zdp22Urdt8h2zC1zYFPDsT?