Bugzilla is not a program, but a website, much the same in concept as the issue reporting part of GitHub.
On either of those you need to have an account, and you then need to get to the correct project (e.g., Thunderbird or NVDA, respectively) to file a bug report. I do not have the actual steps memorized, and if someone has a first bug they want to report I would be happy to set up a time were I could remote in to your computer, as well as have a phone call going, where I can walk you through it and document the steps taken. They vary depending on what system is used to report the bug.
I have wanted to continue my tutorial series on GitHub and reporting issues for NVDA, but I haven't had an issue to report in recent months, and I'm certainly not going to create a "fake issue" to try to document the steps to create an issue. Same for Firefox or Thunderbird through Bugzilla.
Brian - Windows 10 Pro, 64-Bit, Version 1909, Build 18363
Power is being told you're not loved and not being destroyed by it.