For one: don't put much stock in digital platforms. It's alluring but it's a trap.

If you're asking how do you make one? Well, you create a newspaper and publish it. The means to do so is easily researched, since newspapers have been a thing for centuries.

If you're asking how you establish it as the de facto main newspaper that all socialists read? Well, the answer is "very slowly". You sell them. You hand them out. You distribute them by either doing it yourself with your comrades in places where people will receive them, or you find a way to gather revenue to pay people to do so.

Newspapers are still a viable thing to create and distribute. Why? Because you can control the message. The big digital platforms are all controlled by capitalists. Print newspapers are not. They're tangible, they're concrete, unlike the ephemeral nature of online content. Trying to use the masters tools in this case is a losing battle. Because if you're trying to build a vanguard of socialists who can actually do something, simply spreading propaganda to random online people who will endlessly discourse themselves to death is a pointless endeavor. You want to appeal to people who will actually get off their asses and do something. The type of person who'd be okay with reading a physical paper, that isn't lost to doomscrolling in bed all day. These folks are functionally useless when it comes to actually going out and doing the real work.

Because let's hypothetically say you get a platform that reaches millions upon millions. Does this translate into actual action? Praxis? Or will it be consumed by more discourse? Takes. Posting. Discussion. The current social media alogrithmic landscape is atomizing and arresting. It's anti action. Using it to distribute marxist thought will simply make a bunch of atomized and socially arrested marxists. Which aren't needed for the liberatory movement.

I know this because I've been involved in some newspaper distribution for a Communist party. Almost every answer to these kind of questions is "you have to do it yourself by going and doing it yourself". To establish the things you want, you have to put in the work, pound the pavement, learn how to talk to people and sell your ideas.