Added clarifying text for instance docs

Added some clarifying text to help make the transition from double clicking Ball.tscn to editing the specific Ball node itself. Now it is clear to first click within the left nav before moving over to the inspector tab.

Author: chellygel

getting_started/step_by_step/instancing.rst

@@ -121,7 +121,7 @@ Let's try this. Double-click ``ball.tscn`` in the FileSystem to open it.
 
 .. image:: img/instancing_ball_scene_open.webp
 
-Select the Ball node. In the Inspector on the right, click on the PhysicsMaterial
+In the Scene dock on the left, select the Ball node. Then, in the Inspector on the right, click on the PhysicsMaterial
 property to expand it.
 
 .. image:: img/instancing_physics_material_expand.webp