This is an open source project and there are many ways to contribute, from writing tutorials or blog posts, improving documentation, adding papers or courses, submitting bug reports and feature requests, or writing code that can be included in itself.
If you have a bug fix, a new feature request, or stuff you'd like to add, first find or open an issue about it. Talk about what you would like to do. There may be someone already working on this, or there may be specific issues that you should be aware of before implementing the changes.