To featured a post we use the Sticky Posts that is default by WordPress.
To sticky a post go to your WordPress panel on Posts, then mouse over on the post title you want to sticky and then click on Quick Edit.
On the options that appears, select Make this post sticky option and then click on Update button.
That’s it, your post should appears on the featured section of your site/blog.
If you want to see all sticky posts, go to Posts and then go to Sticky.
Obs.: this is the default way of featured a post on WordPress, but some themes may be different, depend on the way it was created. So check the theme documentation to know how it works.