There are various ways you can help:
- Answer issues raised
- Propose fix for issues and/or feature requests (through Pull Request)
- Propose new features (through Pull Request)
- Get more involved by becoming a project maintainer
- If you have no time but money, ask on the community forum; people are always looking to contribute to Jupyter through paid jobs
You can involve yourself in only one project or multiple ones depending your appetite (or is it your time).