Assuming you mean for a streaming service/website:
First, you need great and fresh content that appeals to your target demographic. You also need to be strategic with how often you release new content and how you promote it - over-saturating your audience will just make them tune out. In addition to promoting your content, you need to make sure your site/service is user-friendly and easy to navigate; no one wants to waste time trying to figure out how to use your site. Finally, you need to be active and engaging with your audience when they are on your site/service; if they take the time to leave a comment or ask a question, make sure you respond in a timely, polite manner.