WPF BackgroundWorker and Multiple thread

I need a wait screen before a long time process in one of my WPF project. Later I searched out some articles for help:

1: .NET - WPF ProcessingControl en BackgroundWorker

2: WPF Multithreading: Using the BackgroundWorker and Reporting the Progress to the UI.

3: How to use BackgroundWorker to run two threads in background which change UI

4: How to: Use a Background Worker