added clarifying language for file creation instructions

changes/2593.doc.rst

@@ -0,0 +1,2 @@
+adjusted instructions for file creation to include deliberate directions
+for the target directory for helloworld.py

docs/tutorial/tutorial-0.rst

@@ -85,8 +85,8 @@ After a successful installation of Toga you are ready to get coding.
 Write the app
 =============
 
-Create a new file called ``helloworld.py`` and add the following code for the
-"Hello world" app:
+Create a new file called ``helloworld.py`` within your toga-tutorial
+directory and add the following code for the "Hello world" app:
 
 .. literalinclude:: /../examples/tutorial0/tutorial/app.py
    :language: python