There are a couple of things you should do first, before you can use all of Git's power:

• Add a remote to this project: in the Cloud9 IDE command line, you can execute the following commands git remote add [remote name] [remote url (eg. '[email protected]:/ajaxorg/node_chat')] [Enter]
• Create new files inside your project
• Add them to to Git by executing the following command git add [file1, file2, file3, ...] [Enter]
• Create a commit which can be pushed to the remote you just added git commit -m 'added new files' [Enter]
• Push the commit the remote git push [remote name] master [Enter]

That's it! If this doesn't work for you, please visit the excellent resources from Github.com and the Pro Git book. If you can't find your answers there, feel free to ask us via Twitter (@cloud9ide), mailing list or IRC (#cloud9ide on freenode).

Happy coding!