How to display featured posts?
Go to your Blogger dashboard > Posts > add the label Featured* to the 3 posts you want to display in the "Author's Choice" widget.
* Add the label exactly as it's written above - Featured; with a capital first letter. Blogger's labels are case-sensitive, so if you add featured or FEATURED, the posts wont show up in the "Author's Choice" section.
How to display posts from a different label?
Go to your Blogger dashboard > Theme > open the "Author's Choice" widget from the footer > replace Featured with a different label.
Featured posts code
If you delete the code from the widget, you can copy it and add it again:
<div class="featured-posts-wrapper"><div class="featured-posts-wrap">
<h2>Author's <em>Choice</em></h2>
<script type="text/javascript">
var numposts = 3;
var random_posts = !1;
</script>
<script type="text/javascript" src="/feeds/posts/default/-/Featured?published&alt=json-in-script&callback=featuredposts"></script>
</div></div>