Two of my grandkids, Cheyenne and Jake, keep a journal. It's amazing to me that they do this on their own. I wish I had when I was their age, when I think of all the plot ideas, movie scripts, descriptions, settings, characters, personal experiences, that came up each day, and they're mostly gone forever. We think we'll remember, but we don't. Even a dream that fleshes out a story idea, will be gone the next morning. I have to get up in the middle of the night and write it down. My 93-year-old father keeps a meticulous daily journal of everything that happens. His memory is amazing, but if there's any doubt, he'll check his journal.
If you want to write, this is the best way to start. Keeping a journal will expand your creativity in ways you never imagined.