to make changes, simply open or create some file in your local version. If you created a file, you have to do:
git add [new_file_name]
to make git track the file. If you edited an already tracked file, you don't have to add it. Then:
git commit -am [commit_message]
will commit the change. commit_message is something that describes the type of change you made. Good commit messages are descriptive, easy to understand, and correspond well with the actual changes made. Finally:
git pull origin master
git push origin master
will pull the remote code and then push the commit to the repository on Github.
The code that is on the Github server (not the version on your local machine) is the code we will run our tests on. If you don't push a commit, we won't see it and we won't grade it.