I do not know if can I ask here about using Elementor. I know how to put images in posts, but I do not know how to write a little explanation under them. I tried opening a new column and then dragging the Image widget, and under it Heading widget. But I can not move that column inside of my post. It stays at the end of the post.
that is a question for Elementor, but you may want to try editing the Image in your Media Library and adding an Image Caption. If Elenentor behaves like WordPress it should automatically how that caption below the image.