Well the class thing isn't too relevant actually and you still could write in Javascript.

The class gets created for you by default when you create a script. You just have to make sure the class name is the equal to the files name.

And then you add all function into that class. There are default function like Start, Update, OnGUI, etc or you create your own ones (void foo(), int counter() ,etc).

You usually dont have multiple classes in one script file, so it doesn't really matter. Just see it as a border around your functions.