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HOW TO GET BETTER AT WRITING
STUDY, CRITIQUE, AND PRACTICE
What does that mean?
STUDY the writing of other people and the world around you, with a particular focus on things that are similar to what you would like to do. Read books and scripts, watch movies and TV shows, listen to conversations between other people, and observe the world around you.
CRITIQUE your own work, and get critique from other people. Go through old drafts and find things that you like and things that you dislike. What do you think you did well, and what do you think can be improved? Identifying your strengths and weaknesses will allow you to focus on practicing the areas where you're weak.
PRACTICE writing as much as you can. Consistency is more important than quantity or quality here. Try to write every day if you can, even if it's only 100 words. Don't worry about if they're good words or not, the most important thing is developing the "writing muscle" that will allow you to put words down on a page on command. Once you can do that, you'll have something you can critique, which will help you identify what areas you need to study, which will allow you to improve the quality.