This allows the Gutenberg beta version to be added, allowing users to create blocks in Wordpress when creating blog posts.
Basic Blogs are pre-loaded with this plugin. Just click to activate the plugin.
For the Advanced Blog plan, you'll want to look up "Gutenberg", it is further down the page, so look for the logo, Install and Activate.
Once active, the plugin will show up in your Posts and you'll find a Block option in the upper right hand corner.