The sermons page is a special template that is assigned from the Navigation Tree. This page will display all the sermons for the current sermon series. Visitors can filter by Series, Category, Month and Preacher. The sermon template does not have a header image option. Images assigned to individual sermons will display as as the header image of the sermon detail page and should be 949px in width.  To edit the content for the series navigate to Content > Sermons > Series.

Detailed sermon help can be found at http://help.monkcms.com/article/sermons/.