Write 50 words. That's a paragraph.
Write 400 words. That's a page.
Write 300 pages. That's a manuscript.
Write everyday. That's a habit.
Edit and rewrite. That's how you get better.
Spread your writing for people to comment. That's is called feedbacks.
Don't worry about rejection and publications. That's a writer.
When you are not writing. Read.
Read from the writers better than you. Read and perceive.