You can use NuiCamera.ElevationAngle to set the elevation angle of kinect camera. Yea, as mentioned above answer, you can only move up and down.
This is the example in Visual C#
I create a slider to get the value. Kinect Mortor is limited to -27 to 27 degree of rotation only.
<Slider Value = "{Binding ElevationAngle, Mode =TwoWay}" Height="171" Interval="1" IsSnapToTickEnabled="True" Margin="914,536,284,45" Maximum="27" Minimum="-27" Name="slider_tilt" Orientation="Vertical" SmallChange="1" TickPlacement="TopLeft" Width="38" />
Create a button called btnSetTilt and under the button click event, feed the value of slider to Elevation angle. That's it.
private void btnSetTilt_Click(object sender, RoutedEventArgs e)
{
//Set angle to slider_tilt value
nui.NuiCamera.ElevationAngle = (int)slider_tilt.Value;
}