random image header

Hi,

Sorry, it is a noob question.

Using for example twenty-sixteen theme, it was easy to add a random image header to the theme. You just need to go to theme – header (or personalize – image header), then add images, activate random button, and that was done.

I am looking at latest twenty twenty-five theme, and I cannot find anymore how to achieve this looking at theme editor…

Can someone help me ?
Thank you.