GitHub Issues
GitHub provides a ticketing system called issues which allows users to create and track the progress of tasks that need to be done.
When looking to contribute to a project one of the first places to look is their issues section while following the guidance that the authors of the project have provided in their contributing document.
The issue should describe the work that needs to be done and the contributing document should outline the expectations that must be met in order for the work to eventually make its way into the repository.