Give a Name to your panorama control:
<controls:Panorama x:Name="myPanoramaControl" Title="my application" >
and if you need, give a name to panorama items
<controls:PanoramaItem x:Name="firstPanoramaItem" Header="item1">
then in code behind set the properties you need:
myPanoramaControl.Title = "new title";
or
firstPanoramaItem.Header = "new header";
Hope thi help.