For the Git Challenges you just have to follow the instructions closely. From how to create your c9 account to completing the tutorial.

For that you will need git-it to go to the challenges, and git-it verify to check that you completed it correctly. For detailed instructions read them here: http://jlord.us/git-it/index.html

After you learn how to use git, here are other resources to help you learn more about git:

• Creating a New Github Issue
• Git Blame
• Git Merge
• Git Rebase
• Other Git Resources
• Writing Great Git Commit Messages
• Using GitHub Pages for your front end dev projects
• Search your issue on GitHub
• How Issue Mods Work