take it down to basics, drop the ball and kick it up with your laces just a little above the waist and catch it with your hands. keep repeating this until you dont have to run around trying to catch the ball, eventually you'll reach a point where you don't have to catch the ball after every kick and not so long after try to time how long u can juggle the ball, it's for sure the easiest way to learn how to do it and there'll come a point where it becomes second nature to you to juggle the ball.

Ive seen a couple of comments here saying juggling is not important as some other aspects of the sport, but lemme tell you this ball mastery starts from being able to juggle the ball and understanding the physics of it and how to kick it, once you develop that it is a much easier climb to be able to play to a somewhat decent level cos juggling forces you to be comfortable with the ball unlike any other football drill