So I do whatever they ask me but I don't get the point of this.
The point is, that they are meant to teach C++ using example codes.
How do I put this writings to work?
You'll come to realize that as you go on pursuing C++. As of now, as a newbie, take my word that you'll be able to program almost about anything and everything; i.e. once you master C++.
Ok I got the examples but how do you put it to work?
Those examples are probably meant only for educational and teaching purposes. As you go on, you'll be able to write more application-specific code.