As described in the contributing section of the readme, content can be submitted via pull request or by opening a new issue pointing to content that needs to be brought in. This page describes how to add content to a fork of the repository and submit a pull request containing those changes.
git and git BASH
For mac and linux users, you will need the git command line tools. Windows users should install git-for-windows, which includes git BASH, a bash shell emulator.
If you want to type passwords for everything, skip this section and only use the "https" option when setting up remote repositories (lame). If you hate typing your username and password, follow the instructions here to get your ssh key setup on github. Pro tip: If you want to live dangerously and never type passwords, create a passwordles