This website uses a Jekyll theme called uBuild, which was designed to use Forestry's Blocks feature to create modular page layouts.
Forestry's editing docs provide a good overview of how to use the editor.
To create a new landing page, navigate to the pages section and click the Create New Button and select Page. Enter the title for your page, and select Page builder for the front matter template. Start building your page by adding Page Sections from the dropdown.
Without any page sections, your uBuild page is a blank slate! You will likely want to start the page with a Navigation header or a Simple header.