If you want to contributed to a project hosted on GitHub you will find the majority of the projects ask that you do it in the form of a Pull Request. If you want to learn more about how to submit a pull request try this guide.

Do you want to change the user that is automatically selected when committing with git? I having been using Git and Netbeans/PhpStorm for a long time but I had a niggling issue that I finally got around to solving, how to control the default Author and Commiter.