Selecting a featured image will set it apart from the other images loaded into your post, page or ProPhoto gallery in WordPress. Featured images are used in many ways, including:
Facebook previews
blog excerpt views
ProPhoto Grids
featured image widgets
featured image backgrounds
…and more
By default, WordPress will use the first image uploaded to your post/page/gallery when it needs to make a thumbnail. But you can override this by setting a featured image.
When editing a post or page locate the “Featured Image” option area, typically along the right side of your screen. If you don’t see that area, click the menu button on the top right then the Options link and check the box in the popup to show the Featured Image option area in your editor view.
Step 2 : Feature the image
In the media popup, select or upload an image to feature it for your post/page.
Step 3 : Update your post/page
See the Featured Image area in your editor screen to confirm your selection or to change it after the upload process.
Classic Editor
Step 1 : Find and click the “Featured Image” link
When editing a post or page locate the “Featured Image” option area, typically along the right side of your screen. If you don’t see that area, click the Screen Options link at the top right of the page and check the box to show the Featured Image option area in your editor view.
Step 2 : Feature the image
In the media popup, select or upload an image to feature it for your post/page.
You can also feature an image at any time when in the Add Media popup. Just click the Set Featured Image link on the top left of the uploader popup and it will take you to the same area as shown in the above screenshot.
Step 3 : Update your post/page
See the Featured Image area in your editor screen to confirm your selection or to change it after the upload process.