Getting Started | Emacs Dwelling

(use-package simply-annotate
  :bind-keymap ("C-c a" . simply-annotate-command-map)
  :hook (find-file-hook . simply-annotate-mode))

(with-eval-after-load 'simply-annotate
  (add-hook 'dired-mode-hook #'simply-annotate-dired-mode))

The package is available on GitHub on melpa at simply-annotate or https://github.com/captainflasmr/simply-annotate. There is also an Info manual if you run M-x info and search for simply-annotate.