Getting started with the RadListBox control is pretty straightforward.
In order to use RadListBox in your project you have to add reference to the following assembly:
You can include the control in your page by either dragging it from the toolbox in Visual Studio, or manually creating the control. Below is an example of how to create the RadListBox control in code behind and XAML code:
<telerik:RadListBox x:Name="radListBox" Width="200" />
RadListBox listBox = new RadListBox();
More detailed information how to populate RadListBox with some data you could found here.