INotifyPropertyChanged and InotfyCollectionChanged implementation

Question

I am building a Windows desktop application using WPF and C#. I am trying to use the MVVM model but am not able to get my head around with the model and the INotifyPropertyChanged and INotifyCollectionChanged interfaces.

I am detailing below structure of my model, have simplified it to put my question across. One class model. I am getting trades from an external system and inserting them in the database. Once I inserted them in the database, I would like the page showing the trades getting updated with the new trades.

Where and how should I implement the INotifyPropertyChanged and INotifyCollectionChanged interfaces? My model looks something like Page-->View-->ViewModel<--Model.

If this is not clear then I can provide more information.

// ---Model--
public class Trade
{
  private decimal tradeid;
  private decimal securityid;

  public Trade () {}

  // <<public get-set properties for the above 2 items>>
}

// ---ViewModel--

public class TradeVM
{       
  private ObservableCollection<Trade> _tradeList;

  public ObservableCollection<Trades> TradeList
  {
     get
     {
         //getting all rows from database
        _tradeList = new ObservableCollection<TradesDB>(GetAllRows<Trades>(typeof(Trades)).ToList());
     }
     set
     {
         _tradeList = value;
     }
  }

  public TradesVM() {}    
}

// ---View---

public class TradeView
{
  private TradeVM _tradeVM;

  public TradeView()
  {
    _tradeVM = new TradeVM;
  }    

  public void GetTradesFromExternalSystem()
  {
    //call the webservice of externsal system and get the trades and insert them in the database.

  }

  public Ilist<Trade> GetTradesFromDatabase()
  {
     return _tradeVM.TradeList.ToList();    
  }    
}

// ---Page Class displaying Trades to user---

public partial class TradeData : Page
{
    private TradeView _tradeView;

    public TradeData()
    {
        InitializeComponent();
        _tradeView = new TradeView();
        //datagrid datacontext assignment
        this.dgTrades.Datacontext = _tradeView.GetTradesFromDatabase().ToList();    
  }

  private void cmdGetTrades_Click(object sender, RoutedEventArgs e)
  {
      _tradeView.GetTradesFromExternalSystem();
  }   
}

// ---Page---
// --just putting the datagrid population line. rest all is default
<igDP:XamDataGrid Name="dgTrades" ScrollViewer.HorizontalScrollBarVisibility="Auto" ScrollViewer.VerticalScrollBarVisibility="Auto" DataSource="{Binding}" MaxHeight="800"></igDP>