Some theme settings won't show until you're viewing the page in the theme editor preview window to which they relate - product, collection, article and blog settings all fall into this category. Be sure to navigate to the page you want to edit, to see the options available in the left sidebar of the theme customizer!
Please read the Shopify setup article detailing blogs and articles!
Blog pages can show a sidebar on the right hand side. Add content such as blog articles, images, text, customer testimonials or link to your collections.
Sidebar content can be hidden or displayed on mobile devices on a block by block basis. When shown, it will be positioned just above the footer on mobile.
Blog post tags can be used to filter the articles shown. These will be displayed in the sidebar (if used) or at the top of the blog page.
Blog posts (articles)
The blog post or "article" pages also include the option for another sidebar on the right hand side.
As with the blog page and home page sidebars, you can choose which content to add and which is shown on mobile devices.
Tip: Don't forget to create article excerpts
Note that it's not possible to choose different sidebar content for different blog articles. The homepage sidebar and blog sidebars are completely separate.
Enable cart notes to add a box to your cart page where customers can enter order notes.
If the cart is empty, you can select to show some featured products by choosing a collection to encourage your customers to keep browsing your store.