Hi Robert,
thank you very much for your interest in contributing to Veyon! I'm happy to see you're running and promoting Veyon succesfully! You can find the source code of our documentation at https://github.com/veyon/docs - are you familiar with Git? If so, you can clone this repository and enhance the appropriate chapter, e.g. the installation chapter. Afterwards preferably send a pull request so we can merge your changes easily. If this is too complicated for you you can also download the RST file manually, edit it and send it back to me via email.