As an admin, you may have a news feed post that you'd like to keep at the top of the news feed. This can be done by pinning the post. To pin an existing post, click the three dots and select edit. Now select the pinned post option just above the update button.
Now click update. The post will remain at the top of the news feed until it has been unpinned.
You can also click this when creating a new post for the same effect. The most recent post will hold the highest pinned position in the news feed no matter the order they were pinned. This is how you can pin posts in the news feed.