How do you write in a compelling manner?
Write in a conversational tone, and make sure that you're targeting your audience. Use the right words in the right context.
How do you get better at English?
Continually evaluate your work with mentors and peers. Write a lot, and learn from your mistakes.
What's the best way to engage with your audience online?
Build your social media presence, and dive deep into researching your audience's demographics.