Here's how you'd do this.
<h2>1. Find your audience.</h2>
When starting a platform, find out who you're targeting. In this case, this can be people who like other platforms, or that are active on other platforms. This would allow them to come to your's since they are active on many social medias.
<h2>2. Take feedback.</h2>
Some websites allow you to pay a small fee for thousands to answer a survey you make. Some good questions would be like, "how often do you use social media?", "What's one thing you would change on social media?". People have such creative feedback and can be a key to a new platform!
<h2>3. Figure out your plan.</h2>
Figure out if you're doing a Gaming Social Media plan, or what's your main goal? Figure that out, including using people's feedback! Once you have a chart, design etc on what you're doing that would be a great idea for knowing what you're doing! :)
<h2>4. Get the word out.</h2>
Your company is made, you need staff/workers and more users! Find partners, advertisers and much more. Partners are really useful as they would help you succeed. Advertisements are a key to getting more users on your company.
Let me know if you have any questions!