Here’s an interactive tutorial
** Best experienced in Full Screen (click the icon in the top right corner before you begin) **
7 STEPS
1. The first step is to open Dashboard and click All Posts
2. Select one of your posts and click Edit
3. Scroll down and click Set featured image
4. Click Instant Images
5. Scroll down and click on the selected image
6. Scroll up and click Set featured image
7. Click Update