First you need to complete the assignment that you've been asked for and once you cleared this round, you'll have telephonic interview. You just need to convince the interviewer about how much do you know about SEO, keyword research and how do you write the content for any topic.
1) Written test - testing English writing skills and vocabulary. It will be easy to ace and move forward to next level of interview process
2) Face-to-face interview- just basic question and you'll be selected.
Interview questions [1]
Question 1
1) Why do you want to join as a content writer?
2) Where do you stay, will you be able to commute to office?