You would like to see a feature implemented or a bug fixed in SFML? Great! Contributions to SFML are highly appreciated, be it in the form of general ideas, concrete suggestions or code patches.
A few guiding rules have been set up on the SFML website that you should be aware of before opening an Issue or Pull Request. They will help you focus on the important stuff and prevent you from losing (y)our time with requests that are out of SFML's scope, known issues, and so on.
Those rules cover the general scope defined for this project, a coding style, and a precise procedure to report bugs or suggest new features.