Presidio: Sidebars are not displaying
There might be a couple different things happening here.
First, how many posts do you currently have published on the site? Is it less than 3? If so, this is the reason why the sidebar (and maybe interstitials) won't show on your Home Page. In the Presidio theme, elements like the second and third sidebar are hooked into the number of posts in the blog feed on the Home Page, so until you have enough posts (specifically, 3!), those features won't show up.
If you would like to spend some time getting the aesthetic part of the theme ready and making sure the sidebar looks perfect, I would recommend publishing a few test posts, just to flesh out your blog's home page. Then, you can work through the Customizer tabs, and set up all your sidebars and interstitials, AND be able to preview them. After that, simply delete the test posts, and begin publishing your blog posts. Once you've published three blog posts, the features will populate and the theme can work as intended.
Second (and this is an important one!): Sidebars and interstitials will display relative to the number of posts you've publicized on your site. If you just started blogging, you'll need to set your posts per page (under Settings > Reading > Blog pages show at most _ posts) to match the number of posts you have published, or less.
Explanation: Since Presidio has interstitial functionality, it has to check the number of posts per page before adding the sidebar. So if your posts per page number is set to 10 but you only have 3 posts published, it will never publish the sidebar on the home page. You can set it at 3 temporarily, then once you've published more posts, you can update that number, as long as it stays less than or equal to the number of posts you've published.
If you have already published more than 3 posts, and the reading settings are set up correctly, but you are still encountering the issue, just hit reply and let us know and we can continue troubleshooting!