Handling OnPropertyChanged

I'm not well versed in event-based programming. Basically, I'm still stumbling around with it. I'm trying to get something set up, but even with the tutorials, I can't wrap my head around it. What I would like to do (in words) is the following:

1. I have a dataobject where a property changes. I notice this in the setter of the property, and want to raise an event that the property has changed.

2. Elsewhere (in a different class entirely), I want to know that the property on this object has changed, and take some action.

Now I'm sure this is a common enough scenario, but my google-fu is letting me down. I'm simply not understanding http://msdn.microsoft.com/en-us/library/ms743695.aspx.

I have this:

public class ChattyClass {
  private int someMember;

  public event PropertyChangedEventHandler PropertyChanged;

  public int SomeMember {
    get {
      return this.someMember;
    }
    set {
      if (this.someMember != value){
        someMember = value;
        // Raise event/fire handlers. But how?
      }
   }
}

public class NosyClass{
  private List<ChattyClass> myChatters;

  public void addChatter(ChattyClass chatter){
    myChatters.add(chatter);
    // Start listening to property changed events
  }

  private void listner(){
    // I want this to be called when the PropertyChangedEvent is called
    Console.WriteLine("Hey! Hey! Listen! A property of a chatter in my list has changed!");
  }
}

What do I do to wire this up?

Concerning the comment pointing me back to the link:

In the example I see:

protected void OnPropertyChanged(string name)
{
    PropertyChangedEventHandler handler = PropertyChanged;
    if (handler != null)
    {
        handler(this, new PropertyChangedEventArgs(name));
    }
}

What I'm not understanding:

• Why isn't this just calling PropertyChanged(this, new PropertyCHangedEventArgs(name))
• Where does PropertyChanged get assigned?
• What does the assignment look like?