If manually installed, ensure that burnish.el is in your load-path.
To enable burnish-mode whenever an Org file is loaded, add it to org-mode-hook as follows:
(add-hook 'org-mode-hook #'burnish-mode)
Alternately burnish-mode can be invoked in an Org buffer as desired:
M-x burnish-mode RET
With burnish-mode, automated export of an Org file and viewing the result is done on every file save. If this behavior is not desired, then an alternate install is to bind the command burnish.
(keymap-set org-mode-map burnish-export-key #'burnish)
burnish-export-key is a customizable variable whose default value is C-<f5>.