Create Template Based Landing Pages.
We recommend you first test this in a Non-Defaults account.
Start with the samples included in the documentation. Documentation can be found in our Developer's / API tools. Look for the LPTML - Landing Page Template Markup Language section.
Go to you Settings > Landing Pages. From this list of your landing pages, append the URLin the browser with Append the URL in the browser with ?Action=NewTemplate. ( https://yourdomainname/WebForms.aspx?Action=NewTemplate )
Look for the Template Landing Page Icon next to your page name to verify you are creating a Template Landing Page.
From the Preview tab, click ... in the top left corner to get to the edit screen for the content.
This is obscure and relatively hidden since end users won't have to do this.
In the Edit window, you can add your own HTML that you have created, or you can copy and paste one of our pre-built pages.
To build your own page or copy one of ours, follow these instructions: Developer's / API tools. Look for the LPTML - Landing Page Template Markup Language section.