Mandatory #emacs modules that you have to install for #prosewriting before anything else: flyspell-correct and helm from the MELPA package manager. I already meentioned olivetti at startup, and of course orgmode as a major mode. (package-initialize)
(require 'bookmark+)
(require 'ox-md)
(require 'org)
(org-indent-mode)
(require 'olivetti)

(define-globalized-minor-mode my-global-olivetti-mode olivetti-mode
(lambda () (olivetti-mode 1)))

(my-global-olivetti-mode 1)

In #emacs.d config