How to add a banner to DEBUT

53 6 6

I have already added a custom header to my main page. I have a different size banner that I'd like to add to some of the other pages. Can someone please tell me how to do this? My banner image size is:
1920 px 300 px. Is there a way to add it to the drop down menu on "Debut" with an extension page.banner  I have no idea how this is done. Thanks so much.