First, create a new branch by
git checkout -b "my-new-feature"
Then you can implement your new feature or bug fix. After you have done your necessary changes, add your changes to staging area:
git add myChangedFile.py
Then commit your changes:
git commit -m "Change my file for some reason"
Push your changes to your remote repository (Github, Gitlab or some other service).
git push <remote_name> my-new-feature