How to install Multi-project

Multi-project can be installed from the Melpa package repository for Emacs by adding an entry for Melpa. The link below describes how to install Melpa.

https://melpa.org/#/getting-started

Invoking M-x list-packages will list all of the available packages from the Melpa repository. Typing 'i' at the listing for Multi-project and then 'x' will install it.

The other way to install Multi-project is to download the multi-project.el file and add it to the emacs load-path and then 
add the following lines within your .emacs file:

(require 'multi-project)
(multi-project-mode)