A: Hi,
Our knowledge base is a little bit broken at the moment. But if you head over help.rumble.studio and type what you are looking for you should find it :)
Here is the CNAME assistance page : https://24940985.hs-sites-eu1.com/knowledge-base/how-to-use-your-domain-with-rumble-studio

If it still does not make sense you can contact me through the chat in app with screenshots of your DNS provider to get more detailed instructions:)