I'm using the Twenty Twenty One WordPress theme and would like to add an author image below the title and the excerpt in the entry header for all the single-post pages.

Here's a photo of where I'd like the image to go:

It will display the Profile image and name of the author of the posy. This is the default feature in Twenty Twenty One theme.

UPDATE 1:

You can add post author to all post/pages just by editing the page/posts template. Here are the steps to do the same:

1. Go to Appearance->Editor
2. Click on templates
3. Then select Single Post.
4. Edit the template and add Post Author from there to get post author on all posts.

UPDATE 2

You can also add the same programmatically just by following the given below article: https://www.wpkube.com/how-to-add-author-box-in-wordpress-posts/