First get a fresh clone
git clone [repo]
Or if you had the repo already local check the status
git status
Let's create new branch
git checkout -b [new-branch]
Add all you new stuff
git add -A
Commit it
git commit -m "my new module"
Push it
git push origin [new-branch]
Now in github do a pull-request/merge this branch with master or any other branch
Once merged
git checkout master
Pull changes
git pull
Remove branch `git branch -d [new-branch]