First, you need to create your branch locally
git checkout -b your_branch
After that, you can work locally in your branch, when you are ready to share the branch, push it. The next command push the branch to the remote repository origin and tracks it
git push -u origin your_branch
Your Teammates/colleagues can push to your branch by doing commits and then push explicitly
... work ...
git commit
... work ...
git commit
git push origin HEAD:refs/heads/your_branch