custom domain cname works but how to add data in there -> which repository it reads from?

hello I've set up custom domain with example.domain.com but it shows me "nothing to see here". I have two repositories done following way: user.bitbucket.org which works on that http address and second in way: example.domain.com which has the index.html file only (all lowercased) but still my domain doesn't read any data and I don't know where to find good tutorial for that. If you may help
Thank you
Jan