The display settings tab has some great features in it. You'll be able to add accordions, tabs, a table of contents to your post based on the heading styles set up in the body of your post, hide the teaser from the full post view, and Embed HTML. 

For the first 3 items (accordions, heading 3 as tabs, and table of contents) here is what the body of a post using heading 3s looks like as an example since all three will use the same setting: 

You can choose between a heading 3 or a heading 4 to use the accordion and table of contents styling and heading 3 for the tabbed styling. 

Accordions

• Edit the post you'd like to add accordions to. 
• Make sure Heading 3 or Heading 4 is set on the correct places in the body of your post. See above screenshot example.
• Scroll down to the Display settings section of the editor (you may need to turn on Advanced mode at the bottom right of the screen - should turn blue when engaged). 
• You'll see the first two options are "Teaser & overview styles" and "Post page styles." If you want the accordion to show sitewide you'll need to set the accordions in both places. If you just want accordions on the teaser or just on the full post (after you click through from the teaser) - set them separately.
• Open either drop down and select the options you'd like. Here is an example of the accordions set on H3, the initial state is collapsed, and the behavior allows multiple accordions open at once.
  
• Once you save the post you should see the styling take place. 

Tabs by H3

• Edit the post you'd like to turn on tabs by heading 3.
• Scroll down to the Display settings section of the editor (you may need to turn on Advanced mode at the bottom right of the screen - should turn blue when engaged).
• Find the Heading as Tabs section within Display settings. 
• Select "Turn H3s into Tabs"
• Save
  

Table of contents (TOC)

• Edit the post you'd like to turn on tabs by heading 3.
• Scroll down to the Display settings section of the editor (you may need to turn on Advanced mode at the bottom right of the screen - should turn blue when engaged).
• Find the Display TOC section within Display settings.
• Select "Show"
• Save
  

Show teaser

You can also choose to display the teaser content in full post view, or not. This is handy when you want to have different content on the landing page than you do on the full post. For example, your teaser may say, "Click through to read more about this fantastic new widget!" - which of course will be awkward on the full post. So in this instance, you could uncheck this box, and use different text to intro the full post. If you do that, anything above the teaser break will only appear on the landing page, not in the full post.

You can change the "read more" text to say something else. If you leave it blank, your teaser will end with a link that says "Read more" and visitors can click it to see the full post. If you override it they'll see whatever text you enter here.

Embed HTML

The "Embed HTML" fields are handy for including things like iframes and widgets on your site. If you have been given code to embed, you can add it to this field. Then scroll up to the body text field, and add [embed:1], [embed:2], etc. wherever you'd like the content to appear.