You need package.el. Emacs 24 on has package.el bundled.
Enable installation of packages from MELPA by adding an entry to
package-archives after (require 'package) and before the call to
package-initialize in your init.el or .emacs file:
(add-to-list 'package-archives (cons "melpa" "https://melpa.org/packages/") t) (add-to-list 'package-archives (cons "melpa-stable" "https://stable.melpa.org/packages/") t)