Blog template location and modification

Hi, I would like to customise the blog page, I chose to have an entry page where all my posts are displayed but I can’t find the template or functions file that controls the contents of this page. The only setting available to modify on the customiser is the page title. Basically, I want to add a banner on top of the post feed. Here’s the page: http://kankawe.farocomunicacion.com/es/news/

Regards!