Leftism

It looks something like "from each according to their ability, and to each according to their needs."

As to how we get there, and what the specifics of it look like, the short, honest answer is no one person knows, and that's okay. Much like a medieval peasant would've struggled to imagine modern elections, electric tea kettles, or the welfare state, it's really hard to live in the present and imagine a radically different future. The thing is that a radically different future is coming for us, whether we like it or not. Our current lives are not ecologically sustainable. That is going to force change upon us, probably the hard way, and it's going to hurt.

That said, this is a very active area of scholarship and (mostly) healthy debate. There is a wonderful and expansive socialist scholarly tradition, going back centuries, all trying to answer what you asked me. Economists, philosophers, computer scientists, political scientists, and so on have put a lot of really good work into imagining such a future. Some, like Stafford Beer, or Paul Cockshott, have written a lot about how modern digital technologies could enable such a transformation on the large scale. Others, like David Graeber or Rebecca Solnit, have thought deeply about what a human society even is and what we want from it. Still others, notably Mark Fisher, have written about why capitalism feels so inevitable to so many who live in it.

There's one thing we do know: The first step is enough of us agreeing that we want a more just, fair, and equitable future. Many people, especially but not exclusively those with so much of the wealth, don't want that at all.