How do you change a blog template?

I run a nonprofit and therefore do not know much about programming or website design. I am however creating a new website for the nonprofit which is currently at, https://www.aboutfaceinternational.com/wordpress. I have a blog at https://aboutfaceinternational.com/wordpress/one-article-per-day/one-article-per-day-blog. I want to write a title above the blog posts “One Article per Day” but I do not know how to do this. I have gone through the editor and cannot even figure out how to start. If anyone could let me know, it would be greatly appreciated.

-Karyn