Okay kiddo, so have you ever seen iron ore before? It's a type of rock that has a lot of iron inside of it. Well, steel is made from iron (and a few other things), and the finex process is a fancy way of making steel.
So, they take the iron ore and crush it into tiny pieces. Then, they put those pieces into a big machine called a finex reactor. Inside the reactor, they add some other materials - things like coal and limestone - and they heat everything up real hot (like hundreds and hundreds of degrees hot).
As the materials heat up, they start to break down and react with each other. The iron in the ore is turned into liquid iron, which is then drained out of the bottom of the reactor. This liquid iron is very hot and very pure - it doesn't have any of the impurities that normal iron ore would have.
Now that they have liquid iron, they can use it to make steel! They add in other materials like carbon and some other things to make the steel just right. Then, they pour the liquid steel into molds to shape it into the shapes they need - things like beams, pipes, and plates.
And that's how the finex process works! *high five*