Lead Developer
The best way to add something above the blog posts is to use the Page Header add-on in “Appearance > Blog Page Header” – however that’s only one section.
The other option is to use a plugin like to to display posts with a shortcode: https://wordpress.org/plugins/display-posts-shortcode/
Documentation: http://docs.generatepress.com/
Adding CSS: http://docs.generatepress.com/article/adding-css/
Ongoing Development: https://generatepress.com/ongoing-development