With Online Store 2.0 and compatible themes, merchants can add sections directly to the Blog Page template.
By default, all blogs will be assigned to the Default blog template. Create templates and assign them to blogs to have distinct sections for different blog pages.
In order to add sections to this template, first confirm you are using a compatible version.
Compatible Theme Versions
Add a Section to the Default Template
In the theme editor (Customize), use the page selector to open Blogs, then Default blog.
In the left sidebar, click (+) Add section.
Select one of the available sections. Use the search field to search by section name.