Instead of reinventing the wheel, you could just use a pre-existing solution like TwitchNow.
Making a browser add-on as a new programmer is not an easy task. If you’re persistent on making your own, you’d need to research and learn JavaScript as well as research browser add-on tutorials. You can use Google (or any other search engine) to quickly gain access to material on this subject matter. Asking for help here will likely not get you the support you need, since this is a forum for solving issues integrating with Twitch specifically, not general programming support.