Do the tutorials
to learn the basics of
You will not find a tutorial, which does exactly what you are looking for. But doing the tutorials (not only reading a little bit) help you to understand, how things are working.
This is important and this is the first step to do.
in your case you can for example use the SelectionIndex like this
if Spinnner.SelectionIndex = 1
then open another screen Screen1
else if Spinner.SelectionIndex = 2
then open another screen Screen2
alternatively use the Spinner.Selection