The H1 tag is used on the site title (if displayed). To display it part of the homepage you’d need to edit the file responsible with the homepage (normally index.php & content-index when the posts list is displayed).
Thanks for your reply, I had understood that you had to display the title U site to have the tag <h1>, but I am not coder, I do not know how to do it.
I had thought about having a logo and the title of the site, but I don’t see either how to do it.
Does it have an option in the theme to have the logo and the title of the site at the same time?