!! Polymode required Emacs version 25.1 or higher!!

Via package.el

Polymode is available on the two major package.el community maintained repos - MELPA Stable and MELPA.

You can install Polymode, or more commonly a specific polymode, interactively

M-x package-install [RET] polymode [RET] M-x package-install [RET] poly-markdown [RET]
...

In order to see all available polymodes do M-x list-packages [RET] and search for poly- prefix.

To automatically install relevant polymodes put the following lines into .emacs for each polymode that you use:

(unless (package-installed-p 'polymode)
  (package-install 'poly-markdown))

You can pin packages to always install from MELPA stable like follows:

(add-to-list 'package-pinned-packages '(poly-markdown . "melpa-stable") t)

Via use-package

use-package can also be used to install Polymode via the package.el.

(use-package poly-markdown
  :ensure t)

Or from MELPA stable:

(use-package poly-markdown
  :ensure t
  :pin melpa-stable)

For further configuration options with use-package see the official use-package repository or C-h v use-package [RET].

Manually

cd path/to/vc/dir
git clone https://github.com/polymode/polymode
git clone https://github.com/polymode/poly-markdown
...

In .emacs add "polymode" directory and "polymode/modes" to the load path:

(setq load-path
      (append '("path/to/vc/dir/polymode/"  "path/to/vc/dir/poly-markdown/")
              load-path))

Require any polymode bundles that you are interested in. For example:

(require 'poly-markdown)

Activation of Polymodes

Polymodes are functions and can be used just like ordinary emacs modes. Particularly, activate them in files by either registering a file extension in auto-mode-alist

(add-to-list 'auto-mode-alist '("\\.md" . poly-markdown-mode))

or by setting local major mode variable in the header of the file:

   // -*- mode: poly-noweb -*-

Normally you won't need to setup modes yourself as polymode packages register their polymodes with the common extensions automatically. See the documentation of each polymode package.