Our theme uses WPBakery Page Builder plugin, that provides the composition of your page easy and handy.
Install and activate the plugin (Appearance > Install Plugins). Go to WPBakery Page Builder > Role manager and select for which content types Page Builder should be available during post creation/editing.
Note: WordPress 5.x use Gutenberg as a default editor. We would recommend to disable the Gutenberg editor and use WPBakery page builder as the page editor because it’s more advanced.
Video tutorials you can find here.
Note: We would recommend using Backend editor of the WPBakery Page Builder.