Add a predefined text after each blog post

I would like to know how can I add a piece of content onto the blog post layout. What I am trying to achieve is that for a certain type of post (based on category), a specified piece of content would be automatically inserted into the end of the post. How do I achieve that with SiteOrigin? Looks like the page builder only allows me to add rows to the page one post a time rather than creating a page template.

I am using a theme called Focus.

Thank you for your help in advance.