Hey Yui, welcome to Dreamviews! You've already been given some good advice I see. I'd like to add that you could try reading a book. A good one to start with would be Stephen Laberge's Exploring the World of Dreaming or Robert Wagoner's Lucid Dreaming: Plain and Simple. There is also a lot of good information you could find on here in the forums in the tutorials section and other subforums.

Best of luck to you and your dreaming journey