Our contribution guide has a section on how to create issues. The CONTRIBUTING.md proxy currently only states to read the guide if you want to write code.
I created a link to the reporting section for people that only want to report a bug. I also formatted the different points in a list.
You can view the final file here: https://github.com/senny/rails/blob/09fced4ec5db585167143efef746f616c6422fed/CONTRIBUTING.md
refer to the contributing guide on how to create issues.