This is a premium feature available with Astra Pro Addon plugin. To use these Pro features, you need to have the Astra theme along with the Astra Pro Addon installed on your website.
Quick Steps to Create Site Layout using the Site Layouts Module
Step 1: Make sure you have the Astra Pro Addon plugin installed and activated. How to Install Astra Pro Addon plugin?
Step 2: Activate the module from the Astra Options under the WordPress Dashboard > Appearance > Astra Options
Step 3: Visit customizer [ Appearance > Astra Options > Global > Container > Site Layout ] for Site Layout options and settings
You can activate the module from Appearance > Astra Options > Site Layouts.
With Site Layout module, you can manage the overall layout of the website.
Once you activate the module you can find Site Layout setting under Appearance > Customize > Global > Container > Site Layout
The layout chosen will be applied to the outer wrapper of the site. The default layout will be “Full Width”. Options available with Site Layout modules are explained in individual articles linked below.