Large / Highlight Post
This theme allows you to select a post to display in a large full format on the home page right under the recent posts blog feed.
If you want to show this, select “Show” under Appearance > Customize > Front Page > Large / Highlight Post and then select the post you want to display.
Control Content Displayed / Excerpt vs. Full Post Content
This post shows up on the home page, and the entire content of the post is displayed under the post's featured image. If you would like to restrict the content that shows up here, you can use the "more" tag to do so. It will show the beginning excerpts of your post so a reader can click the “Read More” tag to be directed to your full post. More details on how to use the more tag here and here.
Pro only: If you want to hide “Share” buttons for this post, toggle off the “Show Share Links”. The “Jetpack Sharing Integration” section gives details on how to set up the Share links.