Caption

Hi there, I have a problem with captions. I want a caption to appear under the picture the post ist using as the main image (on the top). This caption, however, should not appear on the homepage were all the posts are shown in a teaser/short format.
Where in the backend do I have to put the caption’s text? It doesn’t matter where I put it – it never appears.

Example: https://www.samtundselters.de/2016/02/21/platonow/

Thanks, Judith