Adding a featured image
A Featured Image is a representative picture for your post which is used in a number of areas & functions, like on the homepage, post page, related post areas, recent post widgets, featured area sliders, etc.. so assigning a featured image to your posts is very important.
To assign a Featured Image to a post, navigate to your post’s create/edit screen and look to the bottom-right. Here, you’ll see a box titled “Featured Image” where you can add your desired image. Be sure to update your post when you’re finished.
Additionally, you can set style for your Featured Image in a tab box above titled "Featured Media Options". You can choose between Standard, Large and Fullwidth.