First, get your child more exposure. The more s/he plays or sees chess or even talks about chess, the more s/he will like it, and feels that chess is a part of his/her life and s/he is part of chess. Study, exercises, then hard work will follow more naturally.
Second, learn chess yourself and play along with him/her. A model chess student at home is much more convincing than thousands of words. You can also have better understanding of your child and his/her games. Feel more sympathy when they lose. You can offer better support when there is a temporary setback.
Third, do a lot of research. Read as much as possible. You want to read bios, news, interviews, blogs, etc. You want to find some role models for your child, and study how those young kids are becoming so good in chess. What's in common? What can you simulate? What can you learn? This is hard work, and takes a lot of time. You will try out some methods, or refine some methods. There are many ways to go to Rome. You want to find one that is repeatable, and executable.
Fourth, remove negative thoughts from your mind. Any negative thoughts. Our mind is very powerful, especially negative ones. You don't know how far your child can go. Don't limit it with your negative mind or other people's negative opinions. No one starts out with a mark of world champion. Your child need move forward, work hard, and push upward again and again.
Here, I didn't give you any detailed action instructions. You have to find out by yourself.