Please first search existing bug reports (especially closed ones) for a report that matches your issue.
When reporting a bug, provide full details of your environment, that means, at a minimum, kitty version, OS and OS version, kitty config (ideally a minimal config to reproduce the issue with).
Install the dependencies using your favorite package manager. Build and run kitty from source.
Make a fork, submit your Pull Request. If it's a large/controversial change, open an issue beforehand to discuss it, so that you don't waste your time making a pull request that gets rejected.
If the code you are submitting is reasonably easily testable, please contribute
tests as well (see the kitty_tests/ sub-directory for existing tests, which
can be run with ./test.py).
That's it.