The biggest difference between you and Picasso, or Einstein, or whoever your heroes are is that they out work you. They spend more time in front of a canvas, or guitar, or computer, working away at applying their minds and souls to specific things.
Want to be more creative? Pick a problem you care about and get to work. If you don’t care about anything, your problem isn’t creativity, it’s apathy. If you start things and give up, your problem isn’t creativity, it’s dedication.
Few people in history that we call creatives today read books or took courses on creativity. Instead they apprenticed with masters in a craft and worked with them. They did the grunt work until they had the skills needed to do more sophisticated work. They learned how to develop ideas and deliver finished work by working. There is no other way.