How to change Caption text?

I want to control the space between the image and the caption text. What’s the css class and code in order to control that ?

See link with further description:

Hello Bernhard,

Please try to use the following CSS code.

You can add CSS code to your site with Simple Custom CSS plugin (just copy CSS code and paste it in Dashboard → Appearance → Custom CSS after installing and activating the plugin). Also you can add CSS code directly to style.css file of your child theme.

figure.wp-caption > figcaption.wp-caption-text {
    margin-top: 5px;

Kind Regards, Roman.